Pranayama

 

The fourth stage, or fourth aspect of the tree of Yoga according to Patanjali is the  Pranayama , or  yogic breathing.
Prana   translates as energy, life, vitality, breath.
Ayama  means stretching, prolonging, expanding, restraining, or controlling.

Pranayama is therefore the art of activating, retaining and circulating vital energy by mastering the respiratory movement in terms of inspiration, expiration and suspension of the breath .

Practicing Pranayama requires above all physical and mental preparation obtained through the practice of asanas. 
Indeed the postures purify the different systems of the body, a prerequisite for the consciousness to be able to internalize itself as required by pranayama.
Just as the leaves ventilate the tree and provide it with nourishment for it to grow well, Pranayama nourishes the cells of the body and vivifies the whole organism.

From a spiritual point of view, the practice of Pranayama is a true meditation which offers to those who devote themselves to it with regularity,  inner clarity, the opening of the heart and the tranquility of the mind.