Chloroplasts measure 2 μm - 5 μm in diameter. They are bilayer membrane organelles located in the cytoplasm of plant cells (and cyano bacteria). The outer membrane is smooth while the inner membrane takes the form of stacks of coins called the thylakoid membrane. The thylakoid membrane is divided into coin like structures called grana. The area between the thylakoid and outer membrane is called the stroma.
Each granum consists of one single intricately folded bilayer membrane. The compartments in a granum (the thylakoid lumen) are all inter-connected. The proteins that perform photosynthesis are embedded thylakoid membranes