Here's why:

* Microvilli function: They are tiny finger-like projections that increase the surface area of cells, especially in areas where absorption or secretion is crucial.

* Animal cells: Many animal cells, particularly those involved in absorption (like in the small intestine) or secretion (like in the kidneys), have microvilli.

* Plant cells: Plant cells have different structures for increasing surface area. For example, they have a cell wall and sometimes root hairs.

Let me know if you have any other questions!