Over the 100-year history of modern neuroscience, the way we think about the brain has evolved with the sophistication of the techniques available to study it. Improvements in microscope design and manufacture, together with the development of cell-staining techniques, afforded neuroscientists their first glimpse at the specialized cells that make up the nervous system. Microscopes with more magnifying power enabled them to probe nerve cells in greater detail, revealing distinct compartments. Newer techniques expose the connections between nerve cells, revealing the complex organization of the brain.
Nineteenth-century histologists created some of the first images of nerve cells by chemically stiffening tissue and then immersing it in silver nitrate, randomly staining a small number of cells to make them visible when they were viewed with powerful new light microscopes. The technique revealed the silhouette of the cell body and its network of extensions, and it enabled the great neuroanatomist Santiago Ramón y Cajal to prove that the nervous system consists of cells. He produced the 1899 drawing at left: it shows finely branched Purkinje cells, large neurons in the cerebellum that play an important role in controlling movement.