Since the discovery of the first extrasolar planet - a planet that does not orbit our sun, but another star - in 1995, the search and study of such "new worlds" has become a fascinating and important part of astrophysics. Today, more than 100 exoplanets are known, exhibiting a vast diversity in their properties like mass or distance from the star. We are involved in this field in a double way: First, as a member of the HARPS-Consortium we take part in the observational search for exoplanets using the 3.6 m telescope in La Silla, Chile, and second by theoretical studies of the formation of these objects, using our enhanced core-accretion formation code, trying so to reconcile theory and observation.