The intake of small membrane vesicles from the extracellular fluid is called endocytosis.

Here's a breakdown of the process and some key points:

* Endocytosis is a cellular process where the cell membrane folds inward to engulf substances from the external environment.

* There are different types of endocytosis, but all involve the formation of vesicles (small membrane-bound sacs) that enclose the ingested material.

* Phagocytosis is a type of endocytosis where large particles, like bacteria or cell debris, are engulfed.

* Pinocytosis is another type of endocytosis where the cell takes in fluids and dissolved solutes.

* Receptor-mediated endocytosis is a highly specific process where cells internalize specific molecules by binding to receptors on the cell surface.

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