Through inner attunement, the ancient yogis were able to perceive the energetic basis of all matter. The seven chakras or energy centers comprise their model of the energetic or subtle body. Each chakra is located along the spine, starting at the base and running upwards to the crown of the head. These centers are not visible by naked eyes but are "whirling disks of light" each radiate a specific color and spiritual quality, and are associated with corresponding psychological, physical, and emotional states necessary for the development of the whole person.