SEM (Scanning Electron Micrograph) of human brain cells. Brain cells or neurons are an extensive network of interconnecting dendrites. Cortical neurons make up the brain's cortex (grey matter). The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It covers the cerebrum and cerebellum, and is divided into left and right hemispheres. The cerebral cortex plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. Magnification x1400 at 12 cm wide.