The EUSO experiment, designed to study Extreme Energy Cosmic Rays (EECR)
from space is presented. Euso is a telescope (2.5 m diameter) to be
installed on the Columbus external payload facility of the International
Space Station, looking downward to Nadir to detect the fluorescence
light produced by EECRs in the atmosphere. The Fresnel optics and the
large focal surface covered with multianode PMTs,allow to survey about
200000 square kilometers of the atmosphere, with a target mass of 10 to
the 12 tons of air. The possibility to detect the Cherenkov light
diffuse from ground, in a delayed coincidence with the fluorescence
light, allows us to discriminate between neutrinos and charged particles
interactions. The very high statistics above the energy threshold of
Euso (a few times 10 to the 19 eV) will clearly indicate the existence
of the GZK effect: indeed, in 3 years of data taking, we expect of order
of 70 interactions above 10 to 20 eV if there is the GZK effect, and of
order of 1000 events if there is no effect. Finally, the present status
of the experiment, and its perspectives, will be discussed.