2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35759Lecture given at the workshop "Mathematical aspects of theories of gravitation", Stefan Banach International Mathematical Centre, 7 March 1996. A mini-introduction to critical phenomena in gravitational collapse is combined with a more detailed discussion of the regularity of the ``critical spacetimes'' dominating these phenomena.Latex, 13 pages, submitted to Banach Centre proceedingsGeneral Relativity and Quantum Cosmologytext