The principal substance that makes up the human brain is neurons, which are specialized nerve cells that transmit information throughout the body. The brain is composed of roughly 86 billion neurons interconnected by synapses, which facilitate communication between them. Neurons play a crucial role in processing and conveying sensory information, controlling movement, and enabling complex cognitive functions such as learning, memory, and decision-making. Besides neurons, the brain also contains glial cells, which support, nourish, and protect neurons. The intricate organization and functionality of these cells are essential for the overall health and efficiency of the brain, impacting behavior and mental processes.