The essence of Yoga consists of a vast editorial project whose objective is to gather all the material of articles, lectures, interviews, question and answer sessions and training courses offered by Yogacarya Iyengar. This first volume contains - among other topics - the definition of Yoga, biographical texts of the Iyengar master and the classic exhibition of Yoga by Patanjali. The work, which has been selected, corrected and personally supervised by B.K.S. Iyengar, is destined to become another reference point for both yoga practitioners and those who wish to know and deepen this incomparable spiritual tradition.