2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/149062We briefly review the phenomenology of FCNC, from the very rare $μ/K$, through the medium $b$, to the "pseudo-well-done" case of $b'$, extending to the possibility of large tree level FCNC at weak scale.6 pages, latex (uses sprocl.sty), no figures [NOTE ADDED: Talk presented at FCNC97 Workshop, Santa Monica, USA, February 19--21, 1997]High Energy Physics - Phenomenologytext