An endosome is a membrane-bound compartment within a cell that plays a crucial role in the transport and sorting of molecules. It forms when the cell membrane engulfs extracellular material, creating a vesicle that then matures into an endosome. This process is essential for cellular uptake of nutrients and signaling molecules. Endosomes can be classified into early and late endosomes, each serving different functions. Early endosomes are involved in sorting and recycling materials, while late endosomes are more focused on degradation. They are part of the endocytic pathway, which is vital for maintaining cellular homeostasis and regulating various cellular processes.