Kriya Yoga
In Sanskrit, Kriya means "action." The action that Kriya is referring to is internal action, while Karma is referring to the physical and mental actions.
This technique includes the practices of Kriya Pranayama or breathing exercises, Shuddhi Meditation or purification Meditation and Shuddhi Kriya or purification actions.
We have Paramahansa Yogananda to thank for the vast knowledge of the ancient science of this technique of Yoga that he bestowed to humanity by establishing the Self-Realization Fellowship in 1920. Before Yogananda brought this practice out to the world, before one had to find a Guru who was knowledgeable to learn this practice.
Yogananada viewed this technique the most effective practice for reaching the ultimate goal of Yoga which is the union with the Divine. While other techniques of Yoga work with Prana meaning "life force energy" indirectly, but with this practice the practitioner is able to control Prana with the mind.
Directing Prana up and down Sushumana Nadi or the central Nadi that is in the center of the spine with awareness and intent. Yogananada says that one Kriya takes about a thirty seconds but is equal one year of spiritual growth.
This practice that is said to have the ability to quicken the evolution of humanity. The Yogis of ancient times through there practice discovered that the secret of Cosmic Consciousness is intimately linked with the mastery of the breath. This technique of Yoga provides a Pranayama practice that is specific to this practice.
A technique of Yoga that focuses on the devotion to God and all of creation.
A technique of Yoga that focuses on the knowledge of the Supreme Self and needs a strong willpower and intellect.
A technique of Yoga that focuses on the actions, both mentally and physically. The practitioner goes through life performing acts selflessness for the benefits of other without attachments of any results.