What are the steps involved in pinocytosis?

There are a total of 4 steps involved in pinocytosis. The process of pinocytosis begins with initiation; molecules bind to the receptor on the cell membrane and then send signals to the cell membrane for the forthcoming processes. In step 2, the cell membrane creates small open-ended pockets or folds surrounding the extracellular fluid to be absorbed. The molecules in the extracellular fluid are also caught into these folds. During step 3, the cell membrane starts to connect at the open end of the pocket to form an invagination. In step 4, the pocket of the cell membrane pinches off the cell membrane, and turns into a vesicle to migrate into the cytosol of the cell. Vesicles alternatively may also fuse with the endosome to hydrolyze the particles into smaller molecules.