This is an introductory book for enzymatic study. It has written in order to provide the complete basic as well as standard knowledge in concise form.It is started from introduction to enzymes with its classification. This book also include the kinetic studies for enzymes. Theories involved in enzymatic catalysis have also been discussed along with the mechanism of transition state in detail. A knowledge on single molecule enzymology has also been discussed in the present book which is based on studies of some reference papers. In concise form, this book presents all necessary and basic knowledge about enzymes.