The works of Harry Markowitz and Eugene Faim, the revolutionary views of Franco Modigliani and Merton Miller, the theories of Fisher Black, Myron Scholes and Robert Merton appeared back in the 1950s–1970s, but did not receive recognition from practitioners for a long time. Nowadays, it is difficult to imagine the world of finance without them. They radically changed the nature of financial markets, investment strategies, and led to the emergence of new financial instruments. The author analyzes the process of development of fundamental ideas of financial theory and their impact on the practice of the modern investment world. The book is aimed at students and teachers of economic universities, financiers and a wide range of readers interested in the application of financial theory in practice.