OK, I didn't answer the question did I?
It's an example of dark field transillumination. Essentially the specimen is suspended above a black background and illuminated by light sources at 45% below it. Lots of fiddling around and experimenting involved. You may need some reflectors and gobos to control and direct the light. Most on line references deal with microscopy but it is well explained in Light, Science and Magic (Hunter, Biver and Fuqua, Focal Press 2012), a book I recommend highly if you are interested in creative lighting.