Chloroplasts are typically enclosed by two membranes (an outer and an inner envelope) plus an internal membrane system called the thylakoid membrane. This gives chloroplasts a total of three membrane systems: the outer envelope, the inner envelope, and the thylakoid membranes, which together subdivide the organelle into the intermembrane space, the stroma, and the thylakoid lumen. Some algae and land plants with secondary or complex endosymbiosis can have additional surrounding membranes, but the standard chloroplast in most plants has three distinct membrane systems.