The primordial matter, or prakrti, material nature, consisting of three modes, generates four groups of five. The first group is called elementary and consists of earth, water, fire, air and ether. The second group of five is called tan-matra, referring to the subtle elements (sense objects): sound, touch, form, taste and smell. The third group is the five sense organs for acquiring knowledge: eyes, ears, nose, tongue and skin. The fourth group is the five working senses: speech, hands, feet, anus and genitals. Some say that there are five groups of five. One group is the sense objects, one is the five elements, one is the five sense organs for acquiring knowledge, another is the senses for working, and the fifth group is the five deities who control these divisions.