Structure of Chloroplast
These are the plastids containing chlorophyll (a green pigment). They give green colour to the plant and are mostly found in leaves.
Chloroplasts are oval in shape and have a diameter of 2-10 micrometre and a thickness of 1-2micrometre.
Chloroplast and its structure
1. Envelope:
The chloroplasts are surrounded by a chloroplast envelope, made up of a double membrane (composed of lipids) with outer and inner layers separated by an intermembrane space. The thylakoid membrane is a third internal membrane that is substantially folded and characterised by the presence of closed discs (or thylakoids).
2. Stroma:
The homogenous semi-fluid matrix present inside the membrane is known as stroma (similar to cytoplasm). It contains DNA, 70 S ribosomes, enzymes and other molecules required for protein synthesis.
3. Thylakoids:
It is a collection of membranous sacs surrounded by the thylakoid membrane. These are the places in which the green coloured pigments called chlorophyll is present.
The thylakoids are arranged in stacks known as grana, and each granum contains around 10-20 thylakoids.
4. Grana:

As mentioned above, these are stacks of thylakoids.
The disc form arrangement of thylakoids stacked one above the other are known as grana.
Grana are interconnected by stroma lamella.
Functions of chloroplasts: