Dust particles were collected by the Stardust spacecraft during its fly-by of comet 81P/Wild2 on 2 January 2004 and successfully returned back to Earth on 15 January 2006. Sixteen particles were delivered to Italian team for laboratory preliminary examinations. These data indicate that cometary grains are rich in various and complex organic compounds and show compositional and structural heterogeneities. Longer or less branched aliphatic chains that those observed in the interstellar medium were detected. Cometary carbonaceous material span a range of processing similar to IDPs and the most primitive meteorites ones, indicating the presence of highly ‘primitive’ materials but with a very labile carbonaceous component, mixed with refractory minerals, that has not been observed in meteorites and IDPs. Moreover, hydrated minerals may be present in two particles one of which may also contain carbonates.