Your brain is a 3-pound organ that is 60% fat

Science · Published 29 October 2026 Swipe more like this →

In short: Despite its role as the command center for every human thought and movement, the brain is not a muscle. It is a complex organ composed of billions of neurons and glial cells, relying on a delicate balance of chemical and electrical signals to regulate everything from your heartbeat to your personality.

The human brain is a master of biological engineering, weighing about 3 pounds in the average adult. While it is often associated with high-intensity activity, its composition is surprisingly lipid-rich, consisting of approximately 60% fat. The remaining 40% is a mixture of water, protein, carbohydrates, and salts. Unlike muscles, which contract to create movement, the brain functions by sending and receiving electrical and chemical signals through a vast network of billions of neurons.

Structurally, the brain is organized into gray and white matter, which are distinguished by their cellular makeup. Gray matter, located on the outer portion of the brain, consists primarily of neuron somas (cell bodies) and is responsible for processing and interpreting information. In contrast, white matter is the inner section composed of axons—the long stems that connect neurons—wrapped in a protective coating called myelin. This distinction allows the brain to separate the 'processing' of data from its 'transmission' across the nervous system.

The brain's architecture is divided into three primary regions: the cerebrum, the cerebellum, and the brainstem. The cerebrum is the largest part, housing the cerebral cortex, which is responsible for high-level functions like reasoning, speech, and voluntary movement. It is divided into two hemispheres connected by the corpus callosum. Meanwhile, the brainstem manages autonomic functions like respiration and heart rate, while the cerebellum coordinates balance and fine motor skills. Deep within these structures, specialized areas like the hippocampus manage memory, and the amygdala regulates emotions like fear.

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