What is the internal structure of chloroplast?

A chloroplast is an oval or biconvex shaped, membrane-bound plastid, about 4 - 6 µm in diameter and 1- 3 µm in thickness. Enclosed within the double membrane of the chloroplast are the grana and stroma. Grana are made up of densely-layered stacks of 10 to 20 disc-shaped structures called thylakoids or lamellae. Chlorophylls, the green colored pigment in plants, are found in the thylakoid membranes. Stroma is a colorless, alkaline, protein-rich, aqueous fluid that occupies the space enclosed by the inner membrane of the chloroplast. The thylakoid system or grana is suspended in the stroma along with the chloroplast DNA and ribosomes, starch granules and various proteins.