The practice of yoga and the science of yoga, or yoga bhyasa and yogavidya, are two of the traditional ways that yoga is described. Yoga is a practice (abhyasa) and a science (vidya). While asanas and pranayama are immensely popular and currently the most visible expressions of the practice of yoga, the science of yoga has a deep and ancient history, though it has not enjoyed the same recent popularity on a public scale as postures have. There is a distinction that needs to be made between the Western definition of science and the Sanskrit word vidya, which means both science and knowledge. While both the Sanskritic and Western translations of science incorporate knowledge, understanding, investigation and quantification, the West regards science as examining observable phenomena that can be verified through measurement and data collection, while the Hindu and yogic sciences accept one's inner experience as a valid source of data collection (pratyaksha). The inner experience is, in fact, the primary source of knowledge, while anything that is observed, heard or inferred is secondary (Yoga Sutra, 1.7). As well, the inner source of knowledge may be an immeasurable, something the West does not factor into science. It's hard to measure something that, by definition, is immeasurable. I had heard from my teachers in India for many years that yoga is a process of internal revelation, the Self revealing itself in the conscious awareness of the seeker. Liberation, and even wisdom, are not something to be added to you from the outside, but revealed from the inside. So, to busy oneself collecting data and amassing information, while useful for sharpening the intellect, is not as useful for inner growth. This idea led me to focus on internal practices for the better part of two decades--that is until Western science came knocking on my door and I answered. A scientist named Dr. Marshall Hagins, having been referred to me by a student, wanted to know if I could create a yoga protocol for a study focused on treating hypertension. His hypothesis was that the practices of asanas and pranayama would have a down-regulating effect on hypertension through the actions on the vagus nerve. My interest was piqued.