internal system of chloroplast
The material within the chloroplast is called the stroma, corresponding to the cytosol of the original bacterium, and contains one or more molecules of small circular DNA. It also contains ribosomes; however most of its proteins are encoded by genes contained in the host cell nucleus, with the protein products transported to the chloroplast.
TEM image of a chloroplast
Within the stroma are stacks of thylakoids, the sub-organelles, which are the site of photosynthesis