One of the most exciting developments in astronomy is the discovery of planets around stars other than our Sun. more than 500 exo-planets have now been detected. But how do these planets form, and why are they so different from our own solar system? Whick ingredients are available to build them? Thanks to powerful new telescopes, in particular the Herschel Space Observatory, astronomers are now starting to address these age-old questions scientifically. In this talk, an overview is given of how stars and planets are born in the extremely cold and tenuous clouds between the stars in the Milky Way. These clouds also contain water and a surprisingly rich variety of organic material. Whick chemical compounds do we find in space? How and where was the water formed that is now in our oceans on Earth? Might these organic molecules end up on new planets and form the basis for pre-biotic material and eventually life?