First step towards understanding nature is acquiring knowledge and skills to explore nature at microscopic scale. The methodology and philosophy of atomic physics is the seed of all modern understanding and developments of scientific breakthroughs today. We hope that this book will help the younger minds to understand and acquire skills to explore nature at atomic scale. 

The first unit presents information about early discoveries and mechanical models of nature at atomic scale. The next unit discusses the vector atomic model and related phenomena including the Stern-Gerlach experiment. The third unit deals the theory of fine structure and hyperfine structure. Units IV, V and VI describe the phenomenological understanding of one-electron, alkali and many-electron atoms. It also gives the account of pre-quantum mechanical understanding of atoms. Last unit discusses the production and characteristics of X-rays.

 At the end of every unit few worked-out examples, exercise problems and questions-to-revise are given for better understanding of the topics. We are grateful to our students and friends for their input; they made considerable contribution to whatever merits this book may have.