Roger Penrose was a major key in creating the now-standard model of black holes. In the fourth installment of our six-part interview, we discuss how Penrose first became involved in black holes, as well as his key insights that developed from Einstein, Schwarzschild, and Oppenheimer's findings. Throughout his career, Penrose has challenged conventional wisdom in physics, mathematics, and the philosophy of science. He has tackled some of the most profound questions of the universe: How do quantum