During the Mahabharata war, when Arjuna was under the illusory spell of Maya, Krishna told him about the two forms of God – Kshara and Akshara. All lifeforms and elements are kshara, and the invisible life force in them is akshara. The entity that goes beyond these two forms and stands as the reason for these two forms is Ishvara – God. (as per Mahabharata Bhishmaparva Chapter 39, verse 16-19)