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%\item How common are planets similar to the Earth (Earth-like exoplanets)?  %\end{itemize}  The wealth of data provided by Kepler has revealed an astonishing fact: "When you wish upon a star, you are wishing upon a star with planets" (W. Borucki). There is in  average one planet orbiting every star in the Universe \citep{2013ApJ...764..105S,2012Natur.481..167C}. Just in our Galaxy this means we have 100 billions planets. Since we have about 100 billion galaxies in the Universe, there are about 10,000,000,000,000,000,000,000 =$10^{22}$ planets out there. %To put it in the words of W. Borucki, Principal Investigator of the KEPLER satellite: "When you wish upon a star, you %are wishing upon a star with planets".    This is fascinating, but still it does not tell much about the likelihood of extraterrestrial life. Planets like Jupiter or Mercury are not expected to host life due to their extreme surface conditions. This could well be the rule in the Universe, with Earth being just a lucky shot of nature. The question is then how common are planets that can likely support biological life.