Black holes are one of the most enigmatic objects in our cosmos, with masses of up to a few billion times the mass of our Sun. Most of the present day galaxies if not all harbor black holes of a few million to billion solar masses at their centers. These supermassive black holes are not only observed in the local universe but their presence has been revealed in the infant universe just a few hundred million years after the Big Bang. The largest of these reached a mass of 13 billion solar masses when the universe was only about 800 Myrs old. How these monsters grow to such high masses in such short times is still a mystery. In this talk, I will discuss our current understanding and challenges of forming supermassive black holes. I will talk about various black hole formation mechanisms and particularly focus on the so-called direct collapse model which is emerged as the most promising way to assemble massive black holes. I will show what are the typical masses of direct collapse black holes (DCBHs). I will compare the abundance of DCBHs with the observed number density of supermassive black holes. Finally, I will discuss how to constrain these models with observational data from present and upcoming space and ground missions.