The existence of nerves was recognized very early in the study of the human body. Ancient Greek and Roman scholars conducted primitive studies of the structure of nerves and hypothesized their functions. This research moved forward very slowly, however, because of the special nature of nerve cells. Early scientists recognized the existence of nerve cells and nerve fibers, but were unable to determine how these two were associated with each other. Especially in the brain, the complex network of dendrites and axons makes it difficult to trace the connection between fibers (dendrites and axons) and cell bodies. Two developments were critically important in the advance of knowledge about nerve cells: microscopy and cell staining.

Some of the earliest and most elegant microscopic observations of nerve cells were made by Rudolf Albert von Kölliker in the 1840s. Kölliker was able to see that...