The structures that are formed by stacking of organized flattened membranous sacs in the chloroplasts are Cristae, Stroma, Stroma lamellae, Grana.

Inside the chloroplasts are stacks of discs called thylakoids. They are compared to stacks of coins within the walls of the chloroplast, and they act to trap the energy from sunlight. The stacks of thylakoids are called grana. They are connected with an extensive system of tubules.