I do not know everything of my body. Suppose I am eating, I am eating something. How this eatable substance transforms into vitamin secretion and how it is being distributed all over the body and is supplying the energy? Or take, for example, I have got my hair, but I do not know how many hairs I have got. Is not that a fact? Can you count your hairs, how many hairs you have got? So, so many things we do not know even of our body, although I am claiming that "This is my body."
But there is another living being. He is supreme living being, Kṛṣṇa. He says that, "I know everything of everyone's body." Ksetra-jñaṁ cāpi māṁ viddhi sarva-kṣetreṣu bhārata (BG 13.3). This is the verse. Ksetra-jña means the knower of the body. You are individual knower of your body, I am knower individually of my body. So everyone is knower of his own body. But there is another person, who says that, "I know everything of everyone's body." Kṣetra-jñaṁ cāpi māṁ viddhi sarva-kṣetreṣu bhārata. He is known as Paramātmā.
The individual knower is known as ātmā, or soul, spirit soul.
(aside) Yes. You can sit down on the bench.
Yes. The individual soul is called ātmā. But there is another soul, Supersoul. He is called Paramātmā. Paramātmā is God. Paramātmā is God, but ātmā and Paramātmā, both of them are cognizant. Both of them know things. Just like I know something about my body or I know something about this world. Similarly, there is another ātmā, supreme ātmā, who knows everything of this universe. He is sometimes called God or the Paramātmā or Kṛṣṇa, whatever He . . . according to different language.