Clathrin is a protein that plays a crucial role in the process of endocytosis, where cells take in substances from their environment. It forms a cage-like structure around vesicles, which are small membrane-bound sacs that transport molecules within cells. This structure helps to shape the vesicle and ensures that the right materials are captured and brought into the cell. The clathrin-coated vesicles are essential for various cellular functions, including the uptake of nutrients and the recycling of membrane proteins. Once the vesicle is formed, it can fuse with other cellular compartments, allowing the contents to be delivered where they are needed.