The Devi resides in your brain and in every other part of your body. And not only does she reside in your body, she resides in all the geographical areas where the parts of her body have fallen—known as the 51 Shakti Pīṭhās in ancient lore. All awareness flowing in the macrocosm, the cosmos, and within you yourself in the microcosm, are thus represented.
Nowadays some people expand these things into an infinite number of nyāsās. Why? Because Lalitā is said to be fond of nyāsa (lalitā nyāsa priyā prōktā). In combination with visualizations, the aim of nyāsa is to induce transcendent states. There is even a school of thought that says nyāsās done properly can, all on their own, lead to the ultimate goal.
…nyāsa means paying attention to your body. Holding your mind in a certain place on your body, keeping your awareness fixed there—that is called nyāsa.
What does nyāsa do? Again, it maps your awareness of each body part onto your brain via the specific imagination of each association. When all body parts have been touched in this way, all parts of your brain will have also been energized. Awakened, restful awareness is the result, a state conducive to thought-free meditation. There are many hundreds of ways in which you can perform nyāsās. There are entire chapters of books and scriptures devoted to these various approaches.
Source: "Gifts from the Goddess"
