Spitzer Space Telescope has had many scientific accomplishments in its first 5 years, exceeding all expectations. It has provided an unprecedented view of the infrared sky. Some key findings include detecting water vapor and organic molecules in protoplanetary disks, characterizing the atmospheres of exoplanets, and observing some of the most distant galaxies. The telescope is now entering a new "Warm Mission" phase using its remaining cryogenic coolant, and will continue making contributions through at least 2013.