The scanning tunneling microscope (STM) and the atomic force microscope (AFM), both capable of visualizing and manipulating individual atoms, are the cornerstones of nanoscience and nanotechnology today. The inventors of STM, Gerd Binnig and Heinrich Rohrer, were awarded with the Nobel Prize of physics in 1986. Both microscopes are based on mechanically scanning an atomically sharp tip over a sample surface, with quantum-mechanical tunneling or atomic forces between the tip and the atoms on the sample as the measurable quantities. This book presents the principles of STM and AFM, and the experimental details. Part I presents the principles from a unified point of view: the Bardeen theory of tunneling phenomenon, and the Herring-Landau theory of covalent-bond force. The similarity between those two theories, both rooted from the Heisenberg-Pauling concept of quantum-mechanical resonance, points to the equivalence of tunneling and covalent-bond force. The Tersoff-Hamann model of STM is presented, including the original derivation. The mechanisms of atomic-scale imaging of both STM and AFM are discussed. Part II presents the instrumentation and experimental techniques of STM and AFM, including piezoelectric scanners, vibration isolation, electronics and control, mechanical design, tip treatment and characterization, scanning tunneling spectroscopy, and atomic force detection techniques. Part II ends with illustrative applications of STM and AFM in various fields of research and technology.