Yoga is a native Indian psychospiritual craft. It dates back to antiquity. It was, however, systematized as a distinct school of classical Indian philosophy by Patanjali in his Yoga-Sūtra during second century B.C. This chapter provides a translation of and commentary on each sutra in psychological idiom of the first part of the book called Samādhi Pada. It discusses (a) the background of Patanjali's Yoga, (b) Yoga theory of samādhi, (c) the nature of mind according to Yoga, (d) Yoga concept of God, (e) hindrances to controlling mind, (f) different kinds and categories of samādhi, (g) the goal of yoga and concludes with a summary of the chapter. According to several commentators, this part of Yoga-Sutra contains the quintessence of Yoga. For this reason, it is in a sense central to the Yoga treatise. It addresses more who are relatively advanced and adept in concentrating and focusing their mind than the beginners.