Our body is made up of innumerable living cells and each such cell, according to yoga, contains another subtle cell which controls the biological cell. According to the modern science, our blood consists of more than 75,000,000,000 healthy cells, which float in it and carry the oxygen to all parts of the body to nourish them. These same cells take the nourishment from the blood and provide it to all the organs and tissues, infuse our digestive system, keep the heart-beat regular, heal up the wounds and stop bleeding.

These cells perform all these functions automatically. Yoga believes that these cells can perform all such functions because each cell is “intellectually developed” to some extent. In spite of this intellectual development of these cells, the human mind exercises control over them. They therefore obey the orders of the conscious as well as the sub-conscious mind. Thus, the body is in a natural way under the influence of mind. It is therefore easy to infer from this that for the health and proper growth of the body, a healthy mental attitude and sound mental health are essential.

All elements of nature are in constant motion, i.e., their atoms are vibrating all the time. The entire universe is therefore being spun by a powerful source of energy. This vibrant motion is well organized and well regulated. We may not be able to see this motion, but its existence cannot be denied. Life itself cannot exist and grow without this source of energy. Every element of the universe vibrates vigorously or slowly according to its own individual characteristics. Nature is also in constant vibration; heat and temperature are the other forms of energy like motion. All are in fact the manifestations of the energy which pervades every atom of the universe.

This energy which provides motion to objects and brings about changes in the universe is termed as Prana in Sanskrit. Prana (vital energy) and Akasha (matter) are all pervading. Modern science says that these two basic elements of the universe cannot be destroyed; their quantity therefore cannot be increased or decreased. The concept of yoga is a little different from this.