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A revolution has occurred in the last two decades in the world of astrophysics.   It all started in the early '90s with the discovery of 'new worlds' around other stars. The world 'Extrasolar planet' (or Exoplanet) started being 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 (asinstead  stars do)} orbiting a star other than the Sun. Different methods for capturing the elusive signature of these distant worlds have been used, leading to the discovery of thousands of exoplanets, including systems containing multiple planets orbiting their host star. The most remarkable discoveries came in the last 2-4 years thanks to the KEPLER space telescope that, looking at the tiny dimming induced by the passage of a planet in front of its host star, was able to answer two fundamental questions:  \begin{enumerate}  \item How common are planets?