The Wolfram language is the programming language of Mathematica, used increasingly by scientists due to its ease of learning and user-friendliness. This book focuses on applications of the Wolfram language to applied mathematics, physics and chemistry. Topics discussed are broad and comprehensive, from differential equations and special functions to fractals and chess, from electromagnetism and optics to relativity and black holes. There is also extensive coverage of quantum theory and quantum chemistry, and the book is peppered with more than 200 color graphics to aid visualization of these concepts. The program codes are provided online as Mathematica notebooks, allowing readers to modify them and manipulate the graphics in real time. This book should be a valuable resource for researchers, educators and students in science and computing who can profit from a more interactive form of instruction.