The largest part of the human brain is the cerebrum, which is divided into two hemispheres. Underneath lies the brainstem, and behind that sits the cerebellum. The outermost layer of the cerebrum is the cerebral cortex, which consists of four lobes: the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe. [Related: Nervous System: Facts, Functions & Diseases]
Like all vertebrate brains, the human brain develops from three sections known as the forebrain, midbrain and hindbrain. Each of these contains fluid-filled cavities called ventricles. The forebrain develops into the cerebrum and underlying structures; the midbrain becomes part of the brainstem; and the hindbrain gives rise to regions of the brainstem and the cerebellum.