The atomic force microscope (AFM) was originally utilised for its imaging capabilities. The full potential of the AFM as a three-dimensional force profiling instrument is only now being realised in an increasingly broad range of fields. One of the key requirements for AFM measurements is the quantification of both in-plane and out-of-plane forces acting between the tip and the sample. In this book the procedure for calibration and the various factors to consider when undertaking such studies is outlined with a focus on force-versus-distance and frictional measurements. Examples of surface property analyses, based on the quantification of forces, are shown, with examples ranging from living animal cells to polymeric materials. This book is designed for researchers and students who are interested in carrying out nano scale force measurements in the biological, physical and chemical sciences on a range of systems.