The cerebral hemispheres are the left and right halves of the cerebrum, divided by a deep midline groove, the longitudinal fissure, and joined across it by the corpus callosum. Each half mostly controls and feels the opposite side of the body. [1][2]
The 3D brain needs JavaScript. The text below still says where the cerebral hemispheres are and what they do.
Seen from above and behind, so the brain’s left half is on your left: the left hemisphere is lit in blue, the right in orange. The front (coronal) slice button cuts across both halves. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
The 3D model has no single shape for a hemisphere, so each is lit as its cortex: the frontal, parietal, temporal and occipital lobes, the insula and the cingulate gyrus of that side, 18 shapes per side. The white matter and the deep parts inside each half are left dark; they have their own pages. [1][3]
Grooves that border it, each shown by the parts on either side: the longitudinal fissure (it runs between them).
Where it is
A deep groove along the midline, the longitudinal fissure, divides the cerebrum into the left and right hemispheres; seen from above, it runs from the front of the brain to the back. [1]
Each hemisphere has an outer layer of grey matter, the cerebral cortex, over an inner core of white matter, and holds its own frontal, parietal, temporal and occipital lobe. [1][4]
Overall the two halves are close mirror images with subtle differences: the right is slightly bigger, and some brains show a slight twist, the Yakovlevian torque. [1]
What it does
Each half works the opposite side of the body: voluntary movement is run by the motor cortex on the opposite side, and touch and other sensations from each side are mostly handled by the opposite hemisphere, because the nerve fibres cross over on the way. [2][1]
Language is lateralised to the left hemisphere in 96% of right-handers and 60% of left-handers, the figures Wikipedia gives; Broca’s and Wernicke’s areas, credited with making and understanding speech, are usually found on the left. [2][1]
The right hemisphere carries the emotional tone of speech (emotional prosody) and is needed to pick up sarcasm, while many other abilities, face perception among them, are represented in both halves. [2]
Not supported: the idea that people are “left-brained” or “right-brained”. Wikipedia calls it a widespread myth, citing a 2013 University of Utah study (Nielsen et al.) of resting brain scans from 1,011 people aged 7 to 29, which found no sign of people having a stronger left-side or right-side network overall; lateralisation was a property of particular networks, not of a person. [2][5]
Connections
The corpus callosum, a wide, thick bundle of 200 to 300 million nerve fibres about 10 cm long, joins the left and right hemispheres and carries signals between them; it is the largest white-matter structure in the brain. [6]
The anterior commissure, a far smaller bundle, also crosses the midline and links the two temporal lobes; the corpus callosum is over ten times larger. Another route between the halves is the hippocampal commissure. [7]
Other names
Left hemisphere and right hemisphere are the formal names of the two halves; everyday speech calls them the left brain and the right brain (“left brain right brain”), also the label of the personality myth under What it does. [1][2]
Size
Measured from the model: the cortex of the left hemisphere (blue) fits in a box about 70 mm wide (side to side), 117 mm tall and 180 mm front to back; the right one (orange), about 70 mm wide (side to side), 117 mm tall and 180 mm front to back. Side by side the two halves are about 141 mm wide. These are the boxes they fit in, not their volumes. [3]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.