Are we alone? This question is as old as humankind itself. For millennia, people have turned their eyes to the stars and wondered if there are others like themselves out there. Does life, be it similar to our own or not, exist elsewhere in our Solar System? Our Galaxy? Until 1992, when the first exoplanet was confirmed, it was uncertain whether there were even any planets outside those in our own Solar System. Today we know of over 3000 planets around other stars and thousands of planet candidates. Do any of these planets have conditions that would support life? What conditions favor the formation of terrestrial-class planets in developing planetary systems? NASA can help address these questions by developing missions designed to find and characterize extrasolar planetary systems. If there is life out there, it probably doesn’t look anything like us.