This diagram shows clearly the "subtle system" that we all have inside. This is an ancient diagram of our central nervous system, depicted in India long before the advent of western neurology. 
There are 3 channels and 7 chakras plus a Kundalini in the triangular "Sacrum" bone just above the Muladhara chakra.
This Kundalini energy is awakened through the practice of Sahaja Yoga Meditation. This energy passes through the 5 chakras that lie above it until it reaches the 7th chakra (Sahastrar). Here there are 1000 nerve endings of the central nervous system which get enlightened and nourished by this energy.
The result is that we enter a higher state of awareness known as "Thoughtless Awareness", or "Nirvichar Samadhi" in sanskrit, & feel a cool breeze coming out of the head and the hands and a very deep peace and Bliss or Ecstacy.
This is the first step in the path to "Nirvana" or "Nirvikalpa Samadhi" in which we feel a state best described as "Heaven on Earth", a permanently Joyful, Peaceful state described in all the ancient scriptures.