Endocytosis

Endocytosis is a process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane. The process which is the opposite to endocytosis is exocytosis.

Read more about Endocytosis:  Endocytosis Pathways, Principal Components of Endocytic Pathway, Clathrin-mediated Endocytosis