Book excerpt: This is an overview of single molecule physics, the study of both equilibrium and non-equilibrium properties at the single molecule level. It begins with an introduction to this fascinating science and includes a chapter on how to build the most popular instrument for single molecule biophysics, the total internal reflection fluorescence (TIRF) microscope. It concludes with the Poisson process approach to statistical mechanics, explaining how to relate the process to diverse areas and see how data analysis and error bars are integral parts of science.