The structure of a neuron is closely tied to its function because the location of the dendrites, where it receives inputs, and the location of its axon, through which it connects to other neurons, determine the connections of the cell, which form the circuits that produce behavior. We can label neurons genetically in the intact fish and view their structure anywhere in the brain or spinal cord of the live animal, as shown below.
Imaging structure in the entire nervous system of the living fish. The whole nervous system of a transgenic fish with one class of neuron labeled in green and other neurons labeled in different colors with a technique called Brainbow. The head (brain) is to the right and the spinal cord extends to the left). As the movie zooms in, you can see the details of the structure of individual nerve cells.