An Italian Space Agency satellite devoted to gamma-ray and X-ray astrophysics, and the most compact and low-power science payload ever developed for high-energy astrophysics. The 352-kg craft has highly innovative scientific instruments for observing transient gamma-ray bursts and solar flares as well as more steady sources such as galactic nuclei and pulsars. Launched into low Earth orbit on 23 April 2007 by an Indian PSLV rocket (India’s first commercial launch), the satellite has the smallest inclination (2.5°) ever achieved by a high-energy space mission. The craft was designed for an operative life of only two years, but it celebrated its 50 000th orbit on 30 December 2016 and continues to operate with high efficiency.