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It all started in the mid '90s with the first discovery of new worlds around other stars. The word "Extrasolar planet" (or Exoplanet) became widely used to identify planets\footnote{A planet is a celestial body massive enough to be bounded by its self gravity (unlike a rock or an asteroid, that are kept together by electromagnetic forces), but not massive enough to produce energy through nuclear fusion (as stars do)} orbiting a star other than the Sun. I remember hearing about the discovery of 51 Pegasi b, a giant planet about 50 light years away, on a bus ride to school. I was blown away. That night I could not sleep, my mind racing towards the amazing implications of that discovery. Little I knew that was just the beginning.   As today\footnote{6 February 2014, check \href{http://exoplanets.org/}{exoplanets.org} for the most recent figure} 765 confirmed exoplanets and 3466 exoplanet candidates are known. The most remarkable discoveries came only in the last couple of years thanks to the \href{http://kepler.nasa.gov/}{KEPLER} space telescope. This amazing instrument has been patiently looking for the extremely tiny dimming induced by the passage of a planet in front of its host star, and helped to answer two fundamental questions:  \begin{enumerate} \begin{itemize}  \item How common are planets?  \item How common are planets similar to Earth?  \end{enumerate} \end{itemize}