This chapter contains sections titled: Introduction Measurement of Force Curves Measuring Surface Forces by the Surface Force Apparatus Forces between Macroscopic Bodies Theory of DLVO Forces between Two Surfaces Van der Waals Forces – the Hamaker Constant Electrostatic Force between Surfaces in a Liquid Spatially Resolved Force Spectroscopy Force Spectroscopy Imaging of Single DNA Molecules Solvation Forces Hydrophobic Forces Steric Forces Conclusive Remarks Acknowledgments References