I was going to suggest that, based on the thread title alone, but it might not be quite so appropriate a thing to show a small niece…
Another point to prepare her for - like anatomy, microscopy is not as pretty and precise as textbooks like us to believe. Even if the microscope is good enough to give sharp detail, microbes tend to look more like scribbled black-and-white hand drawings of tiny things jumping around, not glossy multicoloured pretty pictures like science book illustrations - just as real dissection looks more like a bowl of chopped liver rather than the nice colour-coded diagrams from textbooks. Of course, other than the moon, stuff through a home-sized telescope looks nothing like the planetary probles and hubble long-exposure pictures lead us to believe.
If you are lucky, you can get some interesting sights from things like crystals and cells.
The fascinating thing about science is that you can see this stuff for real, not that it looks pretty. Age 6? She will definitely need some help getting some samples prepared to the point where she can see anything notable.
Can you provide a cite for that? I was about four or five years old the first time an individual atom was imaged; I remember my father coming to me with the then-current issue of Science and showing me the picture. I understood what I was looking at, despite being notably disappointed with the resolution. (“Geez, Dad—it just looks like a stupid blob. Why can’t I see the individual protons? And where are the fucking electrons?”)
tap tap tap Is this thing on? … cricket noises …