EUSO-BALLOON is a pathfinder mission for the Extreme Universe Space Observatory on-board the Japanese Experiment Module (JEM-EUSO) mission. Through a series of stratospheric balloon flights performed by the French Space Agency CNES, EUSO-BALLOON will serve as an evolutive test-bench for all the key technologies of JEM-EUSO, as well as other future missions dedicated to the observation of extensive air shower from space. The objectives of EUSO-BALLOON are (1) to perform a full end-to-end test of a JEM-EUSO qualification model consisting of all the main subsystems of the space experiment, (2) measure the critical atmospheric and terrestrial UV background components, and (3) perform the first detection of air-showers by looking down unto the atmosphere.