Black holes are intriguing objects that appear as classical solutions to General Relativity. When GR is coupled to quantum fields, black holes are even more mysterious: Hawking showed forty years ago that black holes radiate and have a temperature and an entropy. In its most direct interpretation, Hawking radiation also leads to the infamous information paradox. In this seminar, I will first explain those concepts of black hole physics. Then I will discuss black hole microstates or 'fuzzballs' and how they could explain black hole entropy, resolve the black hole singularity and remove the information problem. I will go beyond previous successes for supersymmetric black
holes and treat more realistic non-extremal black holes.
