When light hits the back of your eye, a message has to travel to your brain. Bipolar cells are the middle runners in that relay race.
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The back of your eye is lined with a thin layer called the retina (RET-in-uh). It is made of layers of cells.
Bipolar cells sit in the middle layer. Each one has a branch on one end and a branch on the other end. Bi means two, so bipolar means two ends.
When rods and cones catch light, they pass the news to bipolar cells. Bipolar cells pass it on to ganglion cells.
There are many kinds of bipolar cells. Some send a signal when a spot gets brighter, and others when it gets darker. That helps you see shapes and edges.
Scroll up to the 3D model and press Pass the message. Watch it travel from the light catchers up to the ganglion cells.
All of this passing happens in a tiny fraction of a second, every time you look at something!