Although there is great interest in Tantra, very few people understand its real meaning. This book represents a significant milestone in revealing the profound mysteries of Tantra to the modern world. Drawing from his own experience and the works of Je Tsongkhapa and other great Yogis, Geshe Kelsang Gyatso presents an authoritative and comprehensive guide to the four classes of Tantra in general, and to the generation and completion stages of Highest Yoga Tantra in particular.