Those are some fascinating photos. I’m assuming they have color added after, for the microscope ones?
I think they have to use dye to get different features to show up.
Depends. If it says “false color,” that means it was added in post, after the picture was taking, much like space photos with false color.
There’s a couple of options though. You can use a regular dye for a monochromatic result. You can also use fluorescent dyes which respond to blacklights or UV lights and get some interesting results that way. You can also view under different parts of the spectrum (IE IR or UV) and determine color that way.
But yeah, great find! Love SEM images. SEM produces some really breathtaking results.