This book concerns the use of concepts from statistical physics in the description of financial systems. Specifically, the authors illustrate the scaling concepts used in probability theory, in critical phenomena, and in fully developed turbulent fluids. These concepts are then applied to financial time series to gain new insights into the behavior of financial markets. The authors also present a new stochastic model that displays several of the statistical properties observed in empirical data.. "This book is intended for students and researchers studying economics or physics at a graduate level and for professionals in the field of finance. Undergraduate students possessing some familiarity with probability theory or statistical physics should also be able to learn from the book.