Here's why:

* Cytosol is the fluid that fills the inside of a cell, excluding the organelles. It's essentially the intracellular fluid.

* Animal cells have a defined cell membrane and various internal organelles like the nucleus, mitochondria, and Golgi apparatus. All of these structures are suspended within the cytosol.

Therefore, the cytosol is an essential component of animal cells, providing a medium for biochemical reactions and transporting molecules.