2 layers

The grana of the chloroplast consists of chlorophyll pigments and are the functional units of chloroplasts. Stroma is the homogenous matrix which contains grana and is similar to the cytoplasm in cells in which all the organelles are embedded. Stroma also contains various enzymes, DNA, ribosomes, and other substances.

Chloroplasts absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant. Chloroplasts capture light energy from the sun to produce the free energy stored in ATP and NADPH through a process called photosynthesis.

: one of the lamellar stacks of chlorophyll-containing thylakoids found in plant chloroplasts.

A granum (plural grana) is a stack of thylakoid discs. Chloroplasts can have from 10 to 100 grana. Grana are connected by stroma thylakoids, also called intergranal thylakoids or lamellae. Grana thylakoids and stroma thylakoids can be distinguished by their different protein composition.

Photosynthetic pigments (e.g., chlorophyll) are embedded into the thylakoid membrane, making it the site of the light-dependent reactions in photosynthesis. The stacked coil shape of the grana gives the chloroplast a high surface area to volume ratio, aiding the efficiency of photosynthesis.

When stacked, each thylakoid is able to increase their total surface area which allows more electron transport chains to be embedded into each thylakoid membrane.

Thylakoids are assembled into stacks. Thylakoids exist as a maze of folded membranes. The space surrounding thylakoids is called stroma. Thylakoids contain chlorophyll.