Abstract　 　　  

　The possible existence of black holes (BHs) in the Universe is one important theoretical prediction of Einstein's theory of general relativity since 1916. Astronomers and astrophysicists have been collecting more and more evidence for detecting BHs (stellar mass BHs, intermediate mass BHs and supermassive BHs). In the theoretical framework of spherical time-dependent hydrodynamic collapse, we derive the empirical M-sigma relation in the contexts of SMBHs in galactic bulges/elliptical galaxies and IMBHs in globular clusters. Under the approximation of Paczynski-Wiita gravity, we describe and elaborate the possibility of hypermassive BHs (HMBHs of 10 to 1000 billion solar masses) at the center of very massive galaxy clusters.