COPI, or the Coat Protein I, is a type of protein that plays a crucial role in the transport of molecules within cells. It is primarily involved in the formation of vesicles, which are small membrane-bound sacs that carry proteins and lipids to different parts of the cell. COPI is essential for the recycling of proteins back to the endoplasmic reticulum and for the transport of materials to the Golgi apparatus. This protein operates through a process called vesicular transport, where it coats the vesicles that bud off from the Golgi apparatus. By doing so, COPI helps maintain the proper distribution of proteins and lipids, ensuring that cellular functions run smoothly. Its activity is vital for maintaining cellular organization and communication.