The basic principle of the patch clamp technique was soon adapted and extended in various ways after the first publications. Some of these variations allowed measuring completely new parameters (e.g., the capacitance of the membrane), others have made more complex preparations accessible (brain slices, in-vivo measurements) or optimized the technique for large series of measurements (automated patch machines). In this chapter, we will introduce the most important modifications to the patch clamp technique. The aim is to give a brief overview of their purpose and the technical principles.