"Physics of Atoms and Molecules" is a fundamental course being taught to graduate as well as postgraduate students of Physics, Chemistry, Biotechnology and Materials Science. Though a number of books are available on this topic, but here special care has been taken that a common student could understand the course without much efforts in an easily understandable manner. This book discusses about the Models for Atoms, One, Two and Several Valence Electron Atoms, Zeeman and Paschen-Back Effects in One and Two Valence Electron Atoms, Stark Effect, X-ray Spectra, Hyperfine Structure, Breath of Spectral Lines, Rotational Spectroscopy, Infrared Spectroscopy and Electronic Structure of Diatomic Molecules. For these topics, every part is explained with the help of simple exercises and by using simple language.