Perturbation theory is a fascinating and fundamental topic in mathematics and its applications to the natural and engineering sciences. In this workbook, each explicit example is studied and methods introduced, beginning without proof, a learning method very suitable for singular perturbation problems. The text includes an extensive discussion of timescales and apriori knowledge of the presence of certain timescales. This comprehensive introduction to singular perturbation covers a broad range of topics, includes odes' and pde's, boundary value problems, and problems with initial values.