2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/3710We review the unique cosmological implications of the XMM-LSS survey in association with its multi-WL follow-up: (1) Large Scale Structures traced by X-ray clusters and AGNs, optical galaxies, weak lensing as well as Sunyaev-Zel'dovich effect; (2) location of IR star forming galaxies and IR (obscured) AGNs within the cosmic web. The XMM/MegaCam/VIRMOS/SIRTF data base will provide the first comprehensive study of structure formation - from hundreds of Mpc to galaxy scale - in close connection with environmental processes.5 pages, 1 figure, Proceedings of the Conference "Where is the matter?" Marseille, June 2001Astrophysicstext