I'd appreciate any insights or online references that discuss the following: In THE BLACK HOLE WAR (2008) Leonard Susskind says (beginning pg 368) that in the early 1990's Gerard 'T Hooft conjectured that Planck mass was NOT the end of the elementary particle spectrum. 't Hooft argued that the spectrum of particles extends on to indefinitely large mass in the form of black holes...that these are fundamentally no different from an elementary particle.....and that only certain discrete masses are possible there.... Explanation and comments I suspect the last part....discreteness...relates to the discrete nature of the information on the horizon....via the holographic principle, so the mass is 'practically continuous'....but not quite. Susskind mentions that the smallest diameter a one kilogram object can occupy is not Planck size, but rather a black hole of that mass....He mentions the horizon of such a black hole is about 100 million Planck lengths, but even that is a trillion times smaller than a proton....meantime the singularity at the center is essentially a point mass. So I guess even the massive black holes (singularities) at the center of galaxies are smaller than the common elementary particles. We know any black hole can be completely described via mass, charge, angular momentum, and they seem to carry information/entropy....sounds like they might be a "particle". Have 't Hooft or anyone else taken this idea further??