This book describes techniques that allow the measurement of arbitrary velocity gradient components in fluids with high spatial and temporal resolution, e.g. turbulent fluids. The techniques are based on the properties of scattered laser light. The book gives a detailed and rigorous treatment of the physical and mathematical background in a pedagogical presentation accessible to students in physics and engineering. From both the theoretical and experimental points of view, four different schemes are discussed in detail; the schemes differ in the way the velocity of the moving pattern of the scattered laser light is measured.