Sprites, elves, jets… few people know that scientists habitually use such other-worldly words to describe transient luminous events or TLEs, light flashes that occur during active storms just a few tens of kilometers over our heads. Few people also know that storms can act as particle accelerators generating very brief bursts of X-rays and gamma rays. But what are the physical processes and mechanisms behind these phenomena discovered barely 30 years ago? Do they impact the physics and chemistry of the upper atmosphere, the environment or even humans? Such are the questions facing the French Taranis satellite that will be riding aloft during the night of 16 to 17 November atop a Vega launcher from the Guiana Space Center, an all-French mission involving research scientists from CNES, the national scientific research center CNRS, the atomic energy and alternative energies commission CEA and several French universities.