Just as the fire is situated within wood, yet it is separate from wood, it is not the same as wood. In the same way, the spirit soul is within the body, yet it is separate. It is not the same as the other ingredients within this material body.
So, this spirit soul does not mix with the body, but it is subjugated; it is controlled by the sinful association with the three modes of material nature.
That three modes of material nature mix with each other, that makes three different combinations and then again they mix, and then again they mix, and you will come up with 81 different combinations; those are considered to be the principle.
Then, the again so many mixtures in the mode of goodness, in mode of passion and in the mode of ignorance, which create the unlimited varieties of life with in this universe.
All mixtures are the basic three ingredients SATTVA, RAJAS and TAMAS, but the living entity is individual and independent from this mixing. But due to the association with material nature the living entity thinks, “I am the enjoyer of this material world” and thus is bound by the stringent laws of this material world.HH Jayapataka Swami Lecture – Srimad Bhagavatam
Click here to listen to the full lecture.