Abstract　 　　
　 Black holes are not only a theorectical curiosity, but also an astrophysical reality. Compelling evidence has been established for stellar mass black holes formed from the death of massive stars and supermassive black holes in the centers of galaxies. I will talk about recent efforts to discover the long sought intermediate mass black holes through multi-wavelength observations of ultraluminous X-ray sources in nearby galaxies, and describe our efforts to dynamically determine the black hole masses in some ultraluminous X-ray sources. Previous observations have discovered two dozens of stellar mass black holes, but none have masses lower than six solar masses, posing a serious challenge to stellar evolution, black hole formation and supernova explosion theory. I will describe our recent efforts to discover the quiet stellar mass black holes in the Milky Way by combining the GALEX/SDSS/LAMMOST all sky surveys. I will also briefly discuss our work on SN Ia progentitors and stellar spectral classification for the LAMOST spectroscopic survey.