Toxic Staining: The Lethal Metal That Mapped the Brain

In the dimly lit laboratories of the nineteenth century, scientists faced a profound barrier: the human brain was a gelatinous, featureless mass under a microscope. To understand the nervous system, they needed a dye that could highlight individual nerve fibers without destroying them. The solution came in the form of osmium tetroxide, a volatile, incredibly toxic compound derived from the dense...