After 16 years of unveiling the infrared universe, NASA's Spitzer Space Telescope has left a singular legacy. As one of NASA’s four Great Observatories -- a series of powerful telescopes including Hubble, Chandra and Compton that can observe the cosmos in different parts of the electromagnetic spectrum --Spitzer quickly became a pioneer in the exploration of the worlds beyond our human vision. From stars being born to planets beyond our solar system (like the seven Earth-size planets around the star TRAPPIST-1), Spitzer's science discoveries will continue to inspire the world for many years to come.