There are seven chakras, gateways to the kundalini.  There's one at the base of the spine. There's one halfway between the base of the spine and the navel.  There's a chakra at the navel.  There's a chakra in the center of the chest, at about the elevation of the heart.  There's a chakra in the area of the throat, the lower throat, where the neck joins to the torso.  There's a chakra, of course, between the eyebrows and slightly above; the third eye.  And there's a chakra at the top of the head, the crown chakra.  The lower six chakras are connected by the shushimna, the ida and the pingala.  The crown chakra is not connected to the other six.  It's separate.

Each of the chakras, of course, has been described in yogic literature, as being formed of lotuses or petals, and a different number of petals has been assigned to each of the chakras, a different symbolic color, and so on. What really concerns the student is not so much the number of petals or the colors or the plane of attention that a certain chakra is associated with, but rather the simple shifting of energy; how to pull and move the kundalini up the shushimna through each chakra and eventually how to make that jump from the third eye to the thousand petaled lotus, the crown chakra, on the top of the head.

A cautionary note: kundalini yoga, unlike some types of yoga, tends to be a little more dangerous.  Dangerous if it is not practiced correctly.  When practiced correctly, there is no danger at all.  But to prematurely push the kundalini energy through the chakras can cause a variety of ailments, the most common of which is insanity. 

What is insanity?  Insanity is the inability to confine perception to a particular plane of attention.  So, for example, when a person is practicing kundalini yoga, if they were to push their attention too far, too fast, they can gain visions of other worlds.  These visions can be enlightening, beautific, or terribly frightening, depending upon the nature of the  vision and of course, the individual's own reactions to it.  I mean, nothing is really beautiful or fearful, until we decide that it is.  Also, there are various beings that live in other planes of attention that one will see and encounter, in alternate realities. 

 

- "Kundalini Yoga, Haleakala, Maui", On the Road with Rama