The process of cells entering the plasma membrane is called endocytosis.

Here's a breakdown:

* Endocytosis is a cellular process where cells take in substances from their external environment by engulfing them in a portion of their plasma membrane.

* This membrane then pinches off, forming a vesicle that carries the substance into the cell's interior.

There are three main types of endocytosis:

* Phagocytosis: The cell engulfs large particles like bacteria or cellular debris.

* Pinocytosis: The cell takes in fluids and dissolved solutes.

* Receptor-mediated endocytosis: Specific molecules bind to receptors on the cell surface, triggering the formation of a vesicle.

Let me know if you'd like more details on any of these processes!