Although I don’t believe it’s common anymore, x-ray imaging is one method of studying scientific specimens without destroying the animal.
Not only is it useful for scientific study, but it’s beautiful and a great example of where art and science meet.
As of posting this, the California Academy of Sciences has an exhibit of different ways of studying and preserving scientific specimens for study which includes several large reproductions of x-ray photographs.
Even more fascinating about x-rays is that they are actually part of the electromagnetic spectrum – more-or-less a form of light. X-radiation (X-rays) fall from .01 to 10 nanometers of wavelength putting them between ultraviolet light and gamma radiation.
Human eyes have sensitivity to the edge of the ultraviolet range. However, there are some animals who can see ultraviolet and even into the x-ray wavelengths and, indeed, there were some experiments done in the late 19th and early 20th century proving that human eyes adapted to dark could see x-rays. Additionally, when x-rays are strong enough, the ionization of air molecules becomes visible to us.
Dying specimens (usually fish and amphibians) is another antiquated method of study which produces some visually pleasing results.