Over the past twenty years, thousands of planets have been detected around other stars than our sun. A fraction of these ‘exoplanets’ are potentially habitable, i.e. their surfaces could harbour physical conditions suitable to the existence of life. Testing the actual habitability of these planets - and maybe detecting extraterrestrial life along the way - requires detailed spectroscopic characterisations that are beyond the reach of current technology ... except for some Earth-sized planets recently detected around a nearby, faint and tiny star. The lecture will describe their discovery and the fascinating perspectives involved.