Diencephalon

Diencephalon can be understood as a part of the brain. It is situated between the telencephalon and the midbrain. The midbrain is also called embryonic mesencephalon sometimes.  

It is the main vesicle within the brain that is formed during embryogenesis — the process of the formation of human embryos.  

So, the whole development process takes place in the following ways: 

During the first three weeks of development of human embryos, a neural tube is created. This tube forms three main vesicles: - 

1. Prosencephalon 

1. Mesencephalon 

1. Rhombencephalon 

The first vesicle, i.e. Prosencephalon, afterwards gets divided into two parts:- 

1. Telencephalon 

1. Diencephalon 

It is formed from the ectoderm — it is a germ layer and is one of the primary ones.