2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/124853We review issues and methods for diffuse component separation in the context of Cosmic Microwave Background observations. The revised version contains a paragraph on FastICA and its application to CMB component separation, which was missing in the first version.47 pages, lecture paper for the international summer school 'Data Analysis in Cosmology', 6-10 september 2005, Valencia, SpainAstrophysicstext