The structures in biological samples are often very delicate, their structures ruined by all of those treatments: think soap bubbles rather than bones. It does

The structures in biological samples are often very delicate, their structures ruined by all of those treatments: think soap bubbles rather than bones. It doesn't matter how small the structures you can observe are if you can't be sure they haven't been warped and distorted by dehydration, doping with heavy metals like osmium, exposure to vacuum, and being blasted with radiation until it's heated to 150 degrees celsius. Don't get me wrong: electron microscopy is great for mineral samples, and can be used for biological samples subject to some constraints. But you can't examine specimens with it while they're alive.