In order to understand the role of nature vs nurture, isolated galaxies are unique laboratories for testing galaxy formation and evolution. Under isolated galaxies we understand galaxies located in very low density environments. The AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies) involves the identification and study of a statistically significant sample of the most isolated galaxies in the local Universe. I will present in this talk first results of a revision of the isolation degree for the AMIGA sample using the SDSS.