Seed is both the starting and ending point for a vast majority of those engaged in Agriculture. The one UG practical class on "seed vigor" compelled me to learn more and more and forced me to compile a century and quarter work done in the field of seed vigour by national and international institutes which ultimately took the shape of this book duly providing basic principles in Seed vigour for easy understanding of the students, staff and person engaged in seed industry. Questions and Numerical problems were incorporated for the benefit of students. In a country like India bestowed with diversified agro-climatic conditions has rendered seed production of numerous location specific crop varieties feasible. Yet, retention of their viability and germination has become a serious problem and causing much loss to the end users, the farming community. In the present scenario of climate change, which includes the altered temperatures, photoperiods, rainfall and humidity, etc., seed vigor is declining very rapidly with the length of storage. Short periods of storage under adverse conditions too affect seed vigor more than viability and vigor is lost more rapidly than viability. Loss of vigor is more complex than just physical deterioration. Moreover, seed vigor cannot be measured reliably by standard germination test alone., etc. have rendered the sustainability of farmers is in doubt. With altered climatic conditions vigor is being affected prior to the viability and germination. So this is the need of hour for safe guarding the interests of both farmers as end users of seed and those engaged in seed to seed in public and private sectors. This book offers the basic input for learning by covering all important fundamental topics in a systematic manner with principles affecting seed vigour as well as recent advances in seed vigor and is expected to serve the twin purposes as a textbook for introductory course in seed vigor testing for undergraduate students and as a reference book for Post graduate students and Researchers in seed production, processing, packaging and seed marketing industry in general and all those engaged in seed business in particular. The book basically deals with problems related to seed vigor faced by seed industry on one hand end users or farmers on the other and suggest ways and means to solve the problem. This book also focuses on advances in understanding vigor at molecular level in various crops.