Skip to main content
Nederlands
NL
My UM
Open menu
Education
Open Education
Education
Discover our programmes
Open Discover our programmes
Discover our programmes
Bachelor's
Master's
Pre-master's
Professionals
Other courses
Excellence and honours programmes
Maastricht Summer School
Exchange
Rankings
Get to know UM
Open Get to know UM
Get to know UM
Experience UM: Events
Information for parents
Problem-Based Learning
Admission, enrolment & tuition fees
Open Admission, enrolment & tuition fees
Admission, enrolment & tuition fees
Admission
Enrolment
Tuition fees
Visa / legal residence
Financing your studies
Official document requests
Support & guidance for students
Open Support & guidance for students
Support & guidance for students
UM Student Deans
Study advisers
Psychological support
Student wellbeing
Disability support
The InnBetween: Student Chaplaincy
Support for international students
Studying or interning abroad
Career development
Support for student parents
Social Safety for students
Complaints Service Point
The Student Portal
Housing and student life
Open Housing and student life
Housing and student life
Housing in Maastricht
Housing in Venlo
Support for rental issues (Huurteam Zuid-Limburg)
Moving? Register your new address
Coming to the Netherlands from abroad
UM SPORTS
Healthcare & health insurance
Getting involved at UM
Civic engagement and volunteering
Student organisations
Working alongside your studies
Budgeting for your studies
INKOM & introduction days
Parking
Research
Open Research
Research
Our research
Open Our research
Our research
Unifying research themes
Research Information Portal
Data Science @UM
Open Science
Integrity & ethics
Research quality
Distinguished university professors
Professors
Academic ceremonies
Maastricht Young Academy
PhD
Open PhD
PhD
Paid PhD positions
PhD training programmes
Externally funded PhDs
Current PhDs
Contact
Central PhD Candidates Platform
Young Researchers Academy
PhD Office
Research institutes and themes
Graduate schools
About UM
Open About UM
About UM
Our organisation
Open Our organisation
Our organisation
Faculties
Service centres
Other offices
Support the university
Mission & strategy
Facts & figures
UM’s partnerships
Recognitions
Participation & representation
Local Consultative Body
History
Our education
Open Our education
Our education
International learning environment
Problem-Based Learning
Quality assurance in education
EDLAB – Centre for Teaching & Learning
Our research
Our values
Open Our values
Our values
Diversity, Equity & Inclusion+
Sustainability
Recognition & Rewards
Social safety
Working at UM
Open Working at UM
Working at UM
Applying for a job at UM
Employment conditions and development opportunities
Staff
Alumni
Open Alumni
Alumni
Graduated: what’s next?
Networking
Lifelong development
Giving back
Update your data
FAQ
News & events
Open News & events
News & events
Events
Events archive
Corporate events
News
Blog
Podcasts
Open Podcasts
Podcasts
In Gesprek Met...
Sex, Love, Corona
SBE podcast
Café Europa
Data Scientist MINDSETS
Employed
Terra Mosana taal en dialect
Tussen kunst en wetenschap
Alice in Eduland
CouncilCast
Woke as science
UMagazine
Mobile menu main English (EN)
Education
Open Education
Education
Discover our programmes
Open Discover our programmes
Discover our programmes
Bachelor's
Open Bachelor's
Bachelor's
Bachelor’s programme
Open Bachelor’s programme
Bachelor’s programme
Minors
Master's
Open Master's
Master's
Master’s programme
Pre-master's
Professionals
Other courses
Excellence and honours programmes
Maastricht Summer School
Exchange
Open Exchange
Exchange
Arts and Social Sciences
Business and Economics
Center for European Studies
Health, Medicine and Life Sciences
Law
Psychology and Neuroscience
Open Psychology and Neuroscience
Psychology and Neuroscience
Incoming students
Open Incoming students
Incoming students
FPN Exchange Guide
Open FPN Exchange Guide
FPN Exchange Guide
Academic information
Before leaving FPN
Emergencies
Outgoing students
Science and Engineering
Open Science and Engineering
Science and Engineering
University College Maastricht (UCM)
Maastricht Science Programme (MSP)
University College Venlo (UCV)
Department of Advanced Computing Sciences
Rankings
Get to know UM
Open Get to know UM
Get to know UM
Experience UM: Events
Open Experience UM: Events
Experience UM: Events
Bachelor's Open Day
Master’s Open Day
Bachelor's Online Information Sessions
Master's Online Information Sessions
Study information events
Teenzcollege
Online bachelor’s videos
Information for parents
Problem-Based Learning
Admission, enrolment & tuition fees
Open Admission, enrolment & tuition fees
Admission, enrolment & tuition fees
Admission
Open Admission
Admission
Free, selective and fixus programmes
Handling fee
Using your existing DigiD from abroad
Withdrawing your application
Enrolment
Open Enrolment
Enrolment
Certified copy of your diploma and UM Graduation Statement
UM email account, UM card, Certificate of Enrolment
Re-enrolment: bachelor’s and master’s
Graduation
Add teaching timetables to your calendar
Suspending your studies
Terminating your studies
UM regulations
Tuition fees
Open Tuition fees
Tuition fees
Additional regulations for students with a specific resident status
Additional regulations for EU/EEA students following two study programmes
Tuition fees when starting your studies in February
Paying tuition fees
Visa / legal residence
Open Visa / legal residence
Visa / legal residence
Study progress requirements
Applying to UM as a refugee or asylum seeker
Financing your studies
Open Financing your studies
Financing your studies
Dutch student finance (DUO)
Scholarships for international students
International financial aid
Cost of living & financial assistance
Financial support for study delays: UM Student Support Fund
Official document requests
Support & guidance for students
Open Support & guidance for students
Support & guidance for students
UM Student Deans
Study advisers
Psychological support
Student wellbeing
Open Student wellbeing
Student wellbeing
Wellbeing Movement
MoodLift
Disability support
Open Disability support
Disability support
Applying for disability support
Tips for studying with a disability
Disability facilities per faculty or educational unit
FAQ disability support
The InnBetween: Student Chaplaincy
Support for international students
Open Support for international students
Support for international students
International Student Helpdesk (ISH)
International Student Welcome Day
Buddy programme for new international students
Residence permit: extension, replacement, travel
Support for asylum-seeking and refugee students
Studying or interning abroad
Open Studying or interning abroad
Studying or interning abroad
Logistics and Safety
Culture shock
Practical matters
Career development
Support for student parents
Social Safety for students
Open Social Safety for students
Social Safety for students
Ombuds Officer
Sexual Safety
Complaints Service Point
Open Complaints Service Point
Complaints Service Point
Filing an objection
Filing an appeal
Open Filing an appeal
Filing an appeal
Verdicts CBE and CBHO
Filing a complaint
Step-by-step plan for filing an objection, appeal or complaint
Applicable deadlines for objection, appeal or complaint
Reporting undesirable behaviour
The Student Portal
Open The Student Portal
The Student Portal
Instructions
For teaching staff
What's new
FAQ
Contact
Housing and student life
Open Housing and student life
Housing and student life
Housing in Maastricht
Open Housing in Maastricht
Housing in Maastricht
UM Guesthouse
Housing in Venlo
Support for rental issues (Huurteam Zuid-Limburg)
Moving? Register your new address
Coming to the Netherlands from abroad
Open Coming to the Netherlands from abroad
Coming to the Netherlands from abroad
Registering for the first time in the Netherlands
Opening a Dutch bank account
Compulsory health insurance for non-Dutch students
Travelling to Maastricht
Working in the Netherlands as a non-Dutch student
UM SPORTS
Open UM SPORTS
UM SPORTS
Rates
UM running team
Climbing and bouldering
Padel
Physiotherapy
Squash
Swimming
Tennis
Top-level sport
Senior sports
Exercising with a disability
Sports Council MUSST & Student sports associations
House rules
Taking photos or videos
Healthcare & health insurance
Getting involved at UM
Open Getting involved at UM
Getting involved at UM
Student project team
Student Initiative Helpdesk
Civic engagement and volunteering
Open Civic engagement and volunteering
Civic engagement and volunteering
OmniUM dialogue platform
Become a buddy for new international students
Student organisations
Open Student organisations
Student organisations
Overview of student organisations in Maastricht
Supportive UM services for student organisations
Working alongside your studies
Open Working alongside your studies
Working alongside your studies
Student jobs at UM
Budgeting for your studies
Open Budgeting for your studies
Budgeting for your studies
Council and Water Boards tax
INKOM & introduction days
Parking
Research
Open Research
Research
Our research
Open Our research
Our research
Unifying research themes
Research Information Portal
Data Science @UM
Open Data Science @UM
Data Science @UM
Education
News and activities
Community
Vacancies
Contact
Open Science
Open Open Science
Open Science
FAIR principles
Integrity & ethics
Open Integrity & ethics
Integrity & ethics
Scientific integrity
Research data management
Ethics review
Animal experiments
Financial conflict of interest policy
Research quality
Distinguished university professors
Professors
Open Professors
Professors
Arts and Social Sciences
Business and Economics
Health, Medicine and Life Sciences
Science and Engineering
Law
Psychology and Neuroscience
Academic ceremonies
Maastricht Young Academy
Open Maastricht Young Academy
Maastricht Young Academy
Projects
Open Projects
Projects
Growing Up in Science
Interdisciplinary grant
Internationalisation
Lumière × MYA
Outreach
Recognition & Rewards
Social safety
Trainings & workshops
Work pressure and well-being
Members
Alumni
Get involved
PhD
Open PhD
PhD
Paid PhD positions
PhD training programmes
Externally funded PhDs
Current PhDs
Contact
Central PhD Candidates Platform
Young Researchers Academy
Open Young Researchers Academy
Young Researchers Academy
Contact
Workshops
PhD Office
Research institutes and themes
Graduate schools
About UM
Open About UM
About UM
Our organisation
Open Our organisation
Our organisation
Faculties
Open Faculties
Faculties
Arts and Social Sciences
Open Arts and Social Sciences
Arts and Social Sciences
About FASoS
Open About FASoS
About FASoS
Staff
Honorary doctorates
Organisation
Education
Open Education
Education
FASoS Student Ambassadors
Open FASoS Student Ambassadors
FASoS Student Ambassadors
Student Ambassadors Talk 2025-2026
Bachelor events
Master events
Video Impressions
Research
Partnerships
Departments
Open Departments
Departments
History
Literature & Art
Philosophy
Political Science
Society Studies
Contact
Open Contact
Contact
Disability access
Alumni
News, events and stories
Vacancies
Health, Medicine and Life Sciences
Open Health, Medicine and Life Sciences
Health, Medicine and Life Sciences
About FHML
Open About FHML
About FHML
FHML50
Organisation
Open Organisation
Organisation
Departments
Scientific Integrity
Open Scientific Integrity
Scientific Integrity
Research Code Maastricht UMC+
Aspects of scientific integrity
Platform Scientific Integrity FHML/MUMC+
Roadmaps for scientific integrity and social safety
SCIentific INtegrity – In-Depth course (SCIIN-ID)
Education
Open Education
Education
FHML Honours Programme
Skillslab
Research
Open Research
Research
Institutes
Facilities
Open Facilities
Facilities
Animal experiments
Open Animal experiments
Animal experiments
Legislation and regulation of animal testing
Procedure
Maastricht University Animal Ethics Committee
Services
Open Services
Services
Grants Office
Open Grants Office
Grants Office
National funding opportunities
Funding Health Foundations
Funding for mobility and travel grants
Regional funding opportunities
European funding opportunities
International funding opportunities
Courses
Internal Maastricht UMC+
TKI-PPS
Procedures
Open Procedures
Procedures
Ethics Review Committees
Nagoya Protocol
Prizes and Awards
Research Quality
Partnerships
Facilities
Open Facilities
Facilities
Accessibility campus
Radiation Protection Unit Randwyck
Open Radiation Protection Unit Randwyck
Radiation Protection Unit Randwyck
Procedures
Education
Open Education
Education
SMSR
Open SMSR
SMSR
Programme
TMS-VRS D
Open TMS-VRS D
TMS-VRS D
Programme
TMS-MR
Refresher course TMS-VRS D
Open Refresher course TMS-VRS D
Refresher course TMS-VRS D
Programme and Planning TMS-VRS D
Refresher course RPE
Open Refresher course RPE
Refresher course RPE
Programme and Planning CD and ACD
Refresher course TMS Röntgen
Open Refresher course TMS Röntgen
Refresher course TMS Röntgen
Programme and Planning TMS-Röntgen
Written internal approval
Annual reports
Permit and policy
PhD at FHML/MUMC+
Open PhD at FHML/MUMC+
PhD at FHML/MUMC+
PhD courses
The Faculty PhD committee (FPC)
FHML Alumni
Open FHML Alumni
FHML Alumni
Lifelong development
Networking
Giving back
Contact
Contact
Faculty of Law
Open Faculty of Law
Faculty of Law
About the Faculty
Open About the Faculty
About the Faculty
Faculty in Focus 2024
Staff
History
Strategy
Organisation
Open Organisation
Organisation
Student Council
Education
Open Education
Education
LAW.next (Postgraduate Education)
Internships
Open Internships
Internships
Videos
Mooting competitions and legal clinics
Open Mooting competitions and legal clinics
Mooting competitions and legal clinics
Mooting competitions
Legal clinics
Open Legal clinics
Legal clinics
Maastricht Mediation Clinic
The Innovator’s Legal Clinic (TILC)
Faculty of Law honours programmes
Open Faculty of Law honours programmes
Faculty of Law honours programmes
Bachelor Honours Programme
MaRBLe@LAW
Research
Open Research
Research
Research programme
Research institutes and research groups
Publications
Open Publications
Publications
PhD theses
Working Paper series
Maastricht University Research Publications
Maastricht Law Series
Maastricht Journal
Law Blogs Maastricht
Maastricht Student Law Review
Maastricht Graduate School of Law
Projects and initiatives
Departments
Open Departments
Departments
Criminal Law and Criminology
Open Criminal Law and Criminology
Criminal Law and Criminology
People
Secretariat / Contact
European Law
Open European Law
European Law
People
Education
Research
Law Support Office / Contact
Foundations of Law
Open Foundations of Law
Foundations of Law
People
Research
Foundations of Law Colloquium
Secretariat / Contact
International Law
Open International Law
International Law
People
Education
Research
Law Support Office / Contact
Private Law
Open Private Law
Private Law
People
Projects
Open Projects
Projects
Guliks Opper Gelre
MARICAP
Secretariat / Contact
Public Law
Open Public Law
Public Law
People
Education
Research
Secretariat / Contact
Tax law
Open Tax law
Tax law
People
Secretariat / Contact
Maastricht Tax Symposia
Alumni
Open Alumni
Alumni
Friends of the Law Faculty
45 Years of Law
Contact us
Open Contact us
Contact us
Disability access
Science and Engineering
Open Science and Engineering
Science and Engineering
Research
Open Research
Research
Research departments
FSE STEM Graduate school
Science Communication Incubator
Publications
Education
Open Education
Education
Accreditations and recognitions
FSE Student Ambassadors
News and events
Organisation
Contact
Open Contact
Contact
Disability access PHS1
Disability access Brightlands Smart Services Campus
Disability access Brightlands Chemelot Campus
Psychology and Neuroscience
Open Psychology and Neuroscience
Psychology and Neuroscience
About FPN
Open About FPN
About FPN
Organisation
Education
Open Education
Education
Master Events @ FPN
Non-degree seeking students
Open Non-degree seeking students
Non-degree seeking students
Contract courses
Contract education for FPN alumni
Subsidiary courses
Psychology in Maastricht
Research
Open Research
Research
ERCPN
Do you want to participate in an FPN study?
M-BIC Lecture Series
Received grants
Research projects at FPN
Open Research projects at FPN
Research projects at FPN
Amazone study
Open Amazone study
Amazone study
Amazone: Information for patients
Amazone: Information for professionals
Genital Pain Project
Open Genital Pain Project
Genital Pain Project
Genital Pain Project | Survey
Eetbuien de baas
SHIFT
Departments
Open Departments
Departments
Methodology and Statistics
Open Methodology and Statistics
Methodology and Statistics
Education
Facilities
Open Facilities
Facilities
Accessibility
Events
Open Events
Events
FPN Experience Days
Open FPN Experience Days
FPN Experience Days
Brain Science Experience Day registration form
Psychologie/Psychology Experience Day registration form
FPN Online master Q&A sessions
Introduction Days at FPN
FPN Complaints & Concerns point
Contact
School of Business and Economics
Open School of Business and Economics
School of Business and Economics
About SBE
Open About SBE
About SBE
SBE Strategy 2026-2028
Departments and Institutes
Organisation and Staff
Working at SBE
The Elinor Ostrom Fund
Disability access
Contact us
For prospective students
For prospective PhD candidates
For academic partners
For business partners
Executive education
Research
Open Research
Research
SBE spearheads
Alumni
Blog
Service centres
Open Service centres
Service centres
Facility Services
Open Facility Services
Facility Services
Accessibility Service Point
Staff
Finance
ICT Service Centre
Open ICT Service Centre
ICT Service Centre
ICT Facilities
We make IT work
Staff
Student Services Centre
Open Student Services Centre
Student Services Centre
Departments
Staff
Access to building SSC
University Library
Open University Library
University Library
About the library
Open About the library
About the library
Organisation
Partnerships
Staff
Opening hours & locations
Contact
Collections
Emergencies
House rules
Usage rules
Other offices
Open Other offices
Other offices
UM Brussels Hub
Open UM Brussels Hub
UM Brussels Hub
EU Public Affairs
Activities
Open Activities
Activities
Events
Past events
Open Past events
Past events
2024 Highlights
2023 Highlights
2022 Highlights
2021 Highlights
News
Education
Open Education
Education
Part-time PhD programmes
Contact
Campus Venlo
Center for European Studies
Open Center for European Studies
Center for European Studies
About CES
CES services
Practical information
Staff
Vacancies CES
Central Research Facilities FHML
Open Central Research Facilities FHML
Central Research Facilities FHML
Central Culture Facilities
Central Glass Sterilisation Department
Radio Nuclides Laboratory
Ultra Centrifuge Lab
Contract Research Centre
DataHub
HSB
Open HSB
HSB
Biological Safety
Buildings
Emergency Response Organisation
Health and Safety
IDEE - Equipment Services
Open IDEE - Equipment Services
IDEE - Equipment Services
Emergency and general information
Purchasing equipment
Changing service contract
Exception
Equipment related problem
Preventive maintenance
Disposing equipment
IDEE - Research Engineering
Open IDEE - Research Engineering
IDEE - Research Engineering
Quickservices
Prototypes
Products
International projects
Open International projects
International projects
i2-CoRT
WearIT4COVID
Expertise
Contact
International Staff Support Office
Knowledge Transfer Office
Open Knowledge Transfer Office
Knowledge Transfer Office
BuSyBee - Hyperegio
Language Centre
Open Language Centre
Language Centre
About us
Course information
Open Course information
Course information
Special offers
PhD training courses
Contact
Vacancies Language Centre
Disclaimer and Privacy Statement
Frequently asked questions (FAQs)
Maastricht Centre for Entrepreneurship
Maastricht University Office
Open Maastricht University Office
Maastricht University Office
Staff
MEMIC
Open MEMIC
MEMIC
About MEMIC
Partners and clients
Services & Products
Open Services & Products
Services & Products
RDM Consultancy
RDM Practice
RDM Tools
Staff MEMIC
Contact MEMIC
MUNDO
Open MUNDO
MUNDO
MUNDO Projects
Knowledge for Development at UM
Staff
Maastricht Summer School
Studio Europa Maastricht
Studium Generale
Open Studium Generale
Studium Generale
Lectures, Debates and Talkshows
Lecture Series
Film and Art
News
Practical Information
Open Practical Information
Practical Information
Contact
Locations
Staff
Foundation
Disclaimer and Privacy Statement
Archive
UM SPORTS
Maastricht Housing
PhD Office
Open PhD Office
PhD Office
FAQ
Support for PhD Candidates
Support the university
Mission & strategy
Open Mission & strategy
Mission & strategy
Brightlands
Kennis-As Limburg
STEM
Facts & figures
UM’s partnerships
Open UM’s partnerships
UM’s partnerships
Networks
Open Networks
Networks
WUN
YERUN
YUFE
Open YUFE
YUFE
YUFE for students
YUFE for staff
YUFE for citizens
EASSH
Other partnerships and collaborations
Recognitions
Participation & representation
Open Participation & representation
Participation & representation
Elections
Open Elections
Elections
FAQ Elections
University Council
Open University Council
University Council
Get involved!
About the University Council
Members of the University Council
Local Consultative Body
History
Our education
Open Our education
Our education
International learning environment
Problem-Based Learning
Quality assurance in education
EDLAB – Centre for Teaching & Learning
Open EDLAB – Centre for Teaching & Learning
EDLAB – Centre for Teaching & Learning
Innovating education
Open Innovating education
Innovating education
Education innovation projects
Education consultations
The CCCS principles of PBL education
AI & education at UM
Open AI & education at UM
AI & education at UM
Policy framework for GenAI
Learning Analytics
Professional development for teaching & learning
Researching education
Open Researching education
Researching education
EDLAB Education Research Sounding Board
Video series
Student Guidance at UM
Global Citizenship Education
Students' corner
UM Education Days
edUMinded magazine
Contact EDLAB
Open Contact EDLAB
Contact EDLAB
Meet the team
Mural: State of Siege
Our research
Our values
Open Our values
Our values
Diversity, Equity & Inclusion+
Open Diversity, Equity & Inclusion+
Diversity, Equity & Inclusion+
What we do
Open What we do
What we do
Action against Racism
Our team
Open Our team
Our team
DEI+ Advisory Council
Getting involved
Open Getting involved
Getting involved
Networks for staff and students
Open Networks for staff and students
Networks for staff and students
Female Empowerment
Open Female Empowerment
Female Empowerment
Publications & resources
UM Pride
PAC Network
UnliMited Network
Open UnliMited Network
UnliMited Network
UnliMited-Students
UnliMited-Staff
Disability Inclusion Group
Our stories
Resources & information
Related student organisations
Open Related student organisations
Related student organisations
Feminists of Maastricht
ACMUS
MSA Nour
Inclusive facilities
Open Inclusive facilities
Inclusive facilities
Bloody Serious
DEI Education
Open DEI Education
DEI Education
Inclusive language
Open Inclusive language
Inclusive language
Using gender pronouns in digital communication
Inclusive vacancy guide
Tools & workshops
Moving Conversations Toolkit
Resources & inspiration
DEI Research
Open DEI Research
DEI Research
The Student Retention Study
Diversity in Research Proposals
Helpers and doers
The International Classroom
D&I Grants
Open D&I Grants
D&I Grants
Past D&I Grant winners
DEI+ Academic Calendar
Open DEI+ Academic Calendar
DEI+ Academic Calendar
Dutch culture and local events
Gender Equality Plan
UM Cares
Open UM Cares
UM Cares
UM Cares - Students
UM Cares - Staff
Podcast - Woke as Science
Podcast - Diversity Dialogues
Sustainability
Open Sustainability
Sustainability
Sustainability Team
Open Sustainability Team
Sustainability Team
Green Office
Open Green Office
Green Office
Sustainability Days
Open Sustainability Days
Sustainability Days
FASoS Faculty Day
FHML Faculty Day
FPN Faculty Day
FSE Faculty Day
Law Faculty Day
SBE Faculty Day
Sustainability Festival
Green Teams
Our Ambitions
Our Sustainability Community
Dashboard
Education
Open Education
Education
Minor Sustainability
Research
Open Research
Research
Seed Fund Projects
Operations
Open Operations
Operations
Energy and climate
Real Estate
The WELL Building standard at Tapijn
Food and catering
Mobility
Biodiversity on campus
Open Biodiversity on campus
Biodiversity on campus
Biodiversity challenge
Waste & circularity
Procurement
Sustainable ICT
Other projects
Recognition & Rewards
Open Recognition & Rewards
Recognition & Rewards
FAQ's
UM Career Policy & Compass
Social safety
Open Social safety
Social safety
Sexual safety
Working at UM
Open Working at UM
Working at UM
Applying for a job at UM
Employment conditions and development opportunities
Staff
Alumni
Open Alumni
Alumni
Graduated: what’s next?
Networking
Open Networking
Networking
Alumni events
Alumni stories
Open Alumni stories
Alumni stories
1 study & 3 jobs
Sustainability
Lifelong development
Giving back
Update your data
FAQ
News & events
Open News & events
News & events
Events
Events archive
Corporate events
News
Blog
Podcasts
Open Podcasts
Podcasts
In Gesprek Met...
Sex, Love, Corona
SBE podcast
Café Europa
Data Scientist MINDSETS
Employed
Terra Mosana taal en dialect
Tussen kunst en wetenschap
Alice in Eduland
CouncilCast
Woke as science
UMagazine
Nederlands
NL
My UM
Search
Nederlands
NL
My UM
Search on the website
Dr Ir M.W.J. Huygens