2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54422We review recent work concerning topology changing phase transitions through black hole condensation in Type II string theory. We then also briefly describe a present study aimed at extending the known web of interconnections between Calabi-Yau manifolds. We show, for instance, that all 7555 Calabi-Yau hypersurfaces in weighted projective four space are mathematically connected by extremal transitions.23 pages, 3 postscript figures, uses vanilla.sty, harvmacHigh Energy Physics - Theorytext