Universality of Bharatanatyam
There has been so much written on Indian classical dance, that many people are already familiar with the history and theory of this art. Bharatanatyam became an Indian analogue to western classical dance for me. One of its qualities is universality. The audience of any culture can identify with it above the limitations of the grammar of technique and language of symbols. It is a classical art that not only gives us an entertainment and joy of life, but also carries a mental and spiritual education that serves the evolution of human consciousness. This way its similarities with yoga are very close. Bharatanatyam is one of the most evolved art form, that relates to all the aspects of human existence: body, psyche and the soul.
Body
Let us start with the physical aspect. It is related to Nritta that means an abstract form. As we know it is a combination of various adavus (dance units) with the limited amount of Nritta hastas (hand gestures). All that serves to express pure joy and beauty. But not only. I would like to focus an attention on the arai mandi (half bent knees position) that is the basic of Bharatanatyam. After years of practice I discovered, that the bent knees position, striking the floor plus wormed up body stimulate certain functions in the spinal cord. It influences us in a similar way as some of Yoga asanas. As a result the consciousness of a dancer easily becomes focused and is being elevated slowly on a higher level. No wonder why the first two dance items Allarippu and Jatiswaram are purely abstract.They prepare a dancer for more subtle actions of Abhinaya (expression). 

Navarasa - Nine Sentiments
shown by Prof. Balagopalan
from Kalakshetra Dance Academy in Chennai

click the arrow to see each rasa
 

 Psyche
Abhinaya or nritya is related to human psyche. It is an "expressional" aspect of dance. Its instruments are: the language of gestures (single, double mudras, hastas to depict gods, planets etc...), movements of eyes, head, neck and facial expression. Here different mythological stories are being portrayed through dance compositions like Kautuvam, Kirtanam, Shabdam, Varnam, Javali and Padam. The essence of Abhinaya is the theory of Bhava and Rasa (mood or feelings), that is the basic of Indian aesthetic. An artist "produces" within herself different moods, Navarasa ( 9 sentiments: love, laughter compassion, anger, valour, fear, disgust, wonder and peace) according to the story she dances. These are being shown through the facial expression. These feelings move the hearts of the audience, that for a moment becomes one with the performer.
Soul
Behind the world of feelings and moods rests the "seer", from which all this originated and where all comes back. The dancer created an illusion on stage and at the end, after the firework of a Thillana (concluding dance item) withdraws it all in Mangalam (final prayer). These three aspects, body psyche and soul flow together into the stream of the performance. Every movement has the essence of those three as "Natyasastra" describes it: "Where the hand goes, follows the eye, where the eyes go, follows the heart".