2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/180638After introducing the notion of BPS preons as the basic constituents of M-theory, we discuss the recent negative results in the search for solutions of the D=10 and D=11 supergravity equations preserving 31/32 supersymmetries i.e., of preonic solutions. The absence of these supergravity preonic solutions may point out to a pure quantum nature of BPS preons, manifesting itself in the need of incorporating quantum (stringy/M-theoretic) corrections to the supergravity equations.plain latex, 10 pages. Talk delivered at the Workshop of the RTN network "Constituents, fundamental forces and Symmetries of the Universe", Napoli October 9-13, 2006High Energy Physics - Theorytext