Since several decades we know that most of the matter in the Universe does not consist of the ordinary atoms that we all know. For every gram of ordinary matter there is about five grams of an as yet unknown substance that we call Dark Matter. In this talk Auke-Pieter Colijn will describe the astrophysical evidence that makes us believe that Dark Matter exists. Next he will focus on the strategies that we employ to discover new elementary particles that could be Dark Matter, with a focus on the brand new XENON1T experiment in the underground Gran Sasso laboratory in Italy.