Answer:
Chloroplasts
Step-by-step explanation:
The structures inside plant cells that contain chlorophyll are known as Chloroplasts. This is known to have three membranes two of which are known as ChlorophylI and are the outside membranes. The third membrane which is known as the thylakoid membrane is known to be the inner membrane.
Therefore, in this case, the correct answer is CHLOROPLASTS. It often occurs during photosynthesis in plants.