What are the parts of the brain?

Spinning 3D human brain from the Allen Human Brain Atlas

Your brain is amazing and complex

An intricate powerhouse that keeps you thinking, feeling, and functioning every day 

Did you know that part of your brain is built from the inside out? Have you ever considered why the brain has a wrinkly exterior?

You may be familiar with terms like white matter, grey matter, neurons, and the cerebral cortex—and maybe you’ve wondered what they mean, where they are, or what they do.

Enjoy this visual and informative journey as we explore the brain’s many regions and parts. Scientists at the Allen Institute and around the world are working to uncover the secrets of this remarkable organ — the control center of the body and often considered the most complex object in the known universe.

This image shows an Allen Institute scientist holding a section of human brain tissue used for research.

The Cerebrum

The cerebrum is the largest part of the human brain. It includes structures like the cerebral cortex, the outer-most portion of the cerebrum, that is responsible for things like sensation, motor planning, thoughts, and personality.  
 
Fun fact: “cortex” is Latin for “bark” or “shell.” 

The folds, or wrinkles, in the cerebral cortex serve an important function to increase the amount of brain surface area. Unlike birds and reptiles, most mammals have brain folding, with a few exceptions (e.g., mice). 

Underneath the cerebral cortex, and still within the cerebrum, we have structures like the hippocampus — which is responsible for spatial navigation and memory, and the basal ganglia — which are responsible for reward, motivation, and movement. The basal ganglia are especially important for understanding Parkinson’s Disease (PD), a neurodegenerative disorder with movement difficulties, as this brain area contains unhealthy dopamine neurons in PD.

Brain Stem

The brain stem imagery is courtesy of Society for Neuroscience via brainfacts.org.

Stuff the brain is made of

A closer look beyond the cortex

The brain is mostly made of fat, fluids, and cells. While scientists are interested in all of this matter, many of them have a particular interest in brain cells as they explore how cells impact learning, memory, healthy brain function, and disease. Brain cells are largely divided into neurons, the cells that send electrical signals, and non-neuronal support cells.  

Fun fact: Neurons are born in the inner part of the brain and often migrate outwards past other neurons to get to their final location as the brain grows during development.

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Published March 12, 2025
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