The development of the theory of chaotic dynamics and its subsequent wide applicability in science and technology has been an extremely important achievement of modern mathematics. This volume collects several of the most influential papers in chaos theory from the past 40 years, starting with Lorenz's seminal 1963 article and containing classic papers by Lasota and Yorke (1973), Bowen and Ruelle (1975), Li and Yorke (1975), May (1976), Henon (1976), Milnor (1985), Eckmann and Ruelle (1985), Grebogi, Ott, and Yorke (1988), Benedicks and Young (1993) and many others, with an emphasis on invariant measures for chaotic systems. Dedicated to Professor James Yorke, a pioneer in the field and a recipient of the 2003 Japan Prize, the book includes an extensive, anecdotal introduction discussing Yorke's contributions and giving readers a general overview of the key developments of the theory from a historical perspective.