Osmium is a very dense and hard metal, and it's not typically used in fingerprint analysis. The common methods for visualizing fingerprints under a microscope include:

* Powder dusting: Applying fine powders (like aluminum or black magnetic powder) to the surface where the print is left, making the ridges visible.

* Cyanoacrylate fuming: Exposing the surface to cyanoacrylate vapor (super glue) which reacts with the fingerprint residue, creating a white, visible print.

* Ninhydrin: This chemical reacts with amino acids in fingerprints, turning them a purple color.

* Silver nitrate: This chemical reacts with chloride ions in sweat, making the fingerprint visible.

* Fluorescent powders and dyes: These can be applied to the print and then viewed under UV light for better visibility.

There's no known technique that uses osmium for fingerprint detection in microscopy. If you have any further information about the technique you're interested in, I'd be happy to provide more specific details.