Excess picric acid should be washed out of tissue using several alcohol and water solutions or staining quality may deteriorate over time.

And under the microscope, you can see hundreds of these brown staining blood vessels, capillaries that are feeding cancer cells, bringing oxygen and nutrients.

In 1877, Paul Ehrlich developed a technique of staining blood films which allowed him to describe in detail normal and abnormal white blood cells.

Hinton left a trunk in storage at the Natural History Museum in London that in 1970 was found to contain animal bones and teeth carved and stained in a manner similar to the carving and staining on the Piltdown finds.