"Brain sand" is found in .....

....... plays a very important role in the regulation of a $24$ hours rhythm of our body.

The structure surrounding the pineal gland in the forebrain is located at:

George comes on a vacation to India from the $U.S.$ The long journey disturbs his biological system and he suffers from jet lag. What is the cause of his discomfort?

Where is the pineal gland located?

Select the correct match regarding the source and function of the hormone.