We have pinocytosis, thygocytosis and receptor mediated endocytosis. Let's begin with the most common type of endocytotic process known as pinocytosis. Now, Pinocytosis takes place virtually in every single cell and it's the process by which our cell membrane invaginates and engulfs a relatively small quantity of the extracellular fluid. Now, Pinocytosis is not a specific process meaning it doesn't engulf specific type of molecules. It's basically spontaneous and takes place continuously. And for this reason, we sometimes refer to pinocytosis as cell drinking because it takes place spontaneously and the end result is the uptake of extracellular fluid.