This book explains the basic aspects of symmetry groups as applied to problems in physics and chemistry using a unique approach developed by the author. This approach includes working out symmetry groups and their representations, eliminating the undue abstract nature of group theoretical methods. The author has systematized the wealth of knowledge on symmetry groups that has accumulated in the century since Fedrov discovered the 230 space groups. He reconstructs space groups, unitary as well as antiunitary, based on the algebraic defining relations of the point groups. This work will be of great interest to graduate students and professionals in solid state physics, chemistry, mathematics, geology and those who are interested in magnetic crystal structures.