Final answer:
Immunohistochemistry is used to visualize the whole neuron by attaching a fluorescent label to newly generated cells.
Step-by-step explanation:
The stain used to visualize the whole neuron is called immunohistochemistry.
This technique involves the use of a fluorescent label, such as bromodeoxyuridine (BrdU), which is attached to newly generated cells.
The fluorescent label can then be visualized using fluorescent microscopy, allowing researchers to see the presence of new neurons in brain tissue.