Proplastids are small, undifferentiated organelles found in plant cells. They serve as precursors to other types of plastids, such as chloroplasts, chromoplasts, and amyloplasts. Proplastids are typically located in meristematic tissues, where they can develop into specialized plastids depending on the plant's needs and environmental conditions. These organelles contain a simple structure with a double membrane and a stroma, but they lack the pigments and starches found in more developed plastids. As proplastids mature, they undergo changes that allow them to perform specific functions, such as photosynthesis in chloroplasts or storage in amyloplasts.