Name : Livio Scarsi E-mail : scarsi@ifcai.pa.cnr.it Institute : University of Palermo, Italy and Istituto di Fisica Cosmica con Applicazioni all Informatica, CNR, Via Ugo La Malfa 153, 90146 Palermo Italy TITLE : EUSO : introduction and latest status ABSTRACT : The mission Extreme Universe Space Observatory - EUSO is devoted to the investigation of the Extreme Energy Cosmic Rays ( EECR with E > 5x1019 eV ) and of the High Energy Cosmic Neutrino flux by looking at the streak of UV fluorescence light produced when the particles coming from Outer Space interact with the Earth`s atmosphere. EUSO will observe the fluorescence signal looking downward from Space the dark Earth atmosphere under a 60 degrees full field of view; the Fluorescence light will be imaged by a large Fresnel lens optics into a finely segmented focal plane detector. The segmentation and the time resolution adopted will consent to reconstruct the shower arrival direction and energy with high precision. EUSO is a collaborating effort of research groups from Europe, U.S.A. and Japan and it has been designed to operate for more than 3 years mission life-time; it is expected to detect of the order of 103/year EECRs with E>1020eV and to open a window into the High Energy Neutrino Astronomy. Originally proposed to the European Space Agency as a Free Flyer Low Earth Orbit Mission, EUSO has been approved by ESA in march 2001 in a Phase A Study for a mission on the International Space Station, with a goal for flight in 2007.