The Sakta Agamas, more commonly known as the tantras, declare that the human body is a little universe in itself and that the various tattvas or cosmic principles in creation are there embedded in it. However, each of these tattvas has it own centre of activity, the place where it is most preponderant and from where its energies radiate into the system. They have been called 'cakras' (circles or centres) and have often been likened to lotuses. They are not anatomical centres like the nerve-plexuses but subtle seats of consciousness, of Sakti or divine Power.
Works on Yoga depict fourteen principal nadis or subtle conduits for the flow of pranic energy, of which the susumna, the ida and the pingala are the most important ones. The susumna is situated inside the spinal column and ida and pingala entwine it from left and right. All the three start from the root of the spinal column and end near the centre of the head.
Six cakras are described as being situated in this Susumna. They are muladhara, svadhisthana, manipura, anahata, visuddha and ajna. The seventh, the sahasrara, is the final destination of the Kundalinisakti, the basic power of the human organism which is likened to a coiled serpent lying dormant at the muladhara, until it is roused by appropriate yogic exercises.
The muladharacakra is situated in the space between the anus and the generative organ, at the root of the susumnanadi. It resembles a crimson lotus of four petals. It is the centre of the principle of earth prthvitattva and controls the sense-organ of smell as also feet, one of the organs of action. Brahma, along with his Sakti Savitri, is the presiding deity of this cakra.
The svadhisthanacakra, next in the series, is situated at the root of the genitals and is placed inside the susumna. It resembles a lotus of vermillion colour with six petals. It is the centre of the principle of water the aptattva and controls the sense organ of taste and also the hands from among the organs of action. Visnu along with his Sakti Rakini, is the presiding deity of this centre.
Then comes manipura, at the navel region. It resembles a lotus of dark hue (like the rain clouds) with ten petals. It is the centre of the principle of fire tejastattva-and controls the sense-organ of sight and the organ of action, the anus. Rudra with his Sakti Lakinl is the presiding deity.
The anahata, situated in the region of the heart, resembles a lotus of twelve petals of blood-red colour. It is the centre of the principle of air vayutattva and controls the sense of touch and the genitals. Isa with his Sakti Kakini, is the presiding deity.
Next comes the visuddhacakra, in the region of the base of the throat. It resembles a lotus of sixteen petals of smoky purple colour. It is the locus of the principle of ether akasatattva and controls the organ of hearing as also of speech.
Sadasiva with his Sakini Sakti is the presiding deity.
Last of this series of cakras, often designated as 'satcakras', is the ajnacakra situated in the region corresponding to the middle of the eyebrows. It resembles a lotus of two petals of white colour. It is the centre of the principle of mind. Sambhu with his Sakti Hakini is the presiding deity.
Beyond this there is the sahasraracakra, resembling a white lotus of a thousand petals, presided over by Paramasiva himself. It hangs from the brahmarandhra (opening at the top of the skull) and above the susumna, head downwards.
In fact all these cakras hang head downwards only, until they are pierced by the Kundalini, after it is roused from its slumber by appropriate yogic practices. This piercing of the cakras by the Kundalini is called 'satcakrabheda'. When the Kundalini reaches the sahasrara and gets united with Paramasiva, the yogi will go into samadhi, the superconscious state, experiencing ineffable bliss.
The tantras also describe the various results that accrue to a person who contemplates on these cakras in the prescribed manner.