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 coat around vesicles, which are small membrane-bound sacs that transport molecules within the cell. This coating helps to shape the vesicle and ensures that the right materials are captured and delivered to their intended destinations. The structure of clathrin resembles a triskelion, consisting of three heavy chains and three light chains. When clathrin assembles, it creates a basket-like formation that invaginates the cell membrane, facilitating the budding off of vesicles. This process is essential for various cellular functions, including nutrient uptake and receptor recycling.