What could I do with a microscope?

My parents were awesome enough to get me a microscope when I was a kid, as I was nerdy enough to want one. For fun.
My days of moonlighting as a 10 year old biologist are long over, but, since the thing is still sitting in the closet of my old room, I might as well put it to good use, and what's a better use than beer?
Its a monocular compound microscope, with 3 magnifications (I think 40x, 100x, and 400x, but I can't remember. I'll find out for sure next time I visit my parents).
I'm not sure what type of magnification one needs for yeast, it'd be cool to be able to get viability, or even see what kind of critters I get from wild yeast / bacteria. Could I do anything useful with this?
Thanks,
- Paul

100x is OK for yeast 400 for bacteria, though I can't recall looking without stain, phase contrast or oblique illumination. For oblique, you just sort of put the illumination a little out of alignment so that the light is bent more toward the objective by some things that others.
As for uses, with a little methylene blue and a hemocytometer, you can count living vs dead cells to see how your yeast are.

Well, I was off by a bit for the magnifications. It's 4x, 10x, 40x
Can 40x still be useful?

edit: I forgot about the compound part of the compound microscope. Eyepiece is another 10x. Doy

You can look at bugs 'n shvt!

It's 4x, 10x, 40x

Click to expand...

Are those the numbers on the objective lenses? (Microscope Diagram) If so, look at the Eyepiece/ocular as well. It's usually 10x, if that's the case, your original 40, 100, and 400x were right on.

So, when looking at the yeast, you can then go and change things like nutrients? Would this help you in anyway in brewing or just to check you yeast bank samples?

If you suspect a beer is spoiled a check with a microscope will reveal what type of bug is responsible. If a beer is hazy microscopic examination quickly tells you whether you have yeast in suspension and/or protein-polyphenol globules. If you have gushers you can spot calcium oxalate crystals in the beer if that's the cause. You'll quickly learn what the various strains you use look like when they are healthy. Changes in cell morphology or cells that don't match what you put in are obvious signs of a problem.

Looks like I will be getting a microscope. I wish I knew what to look for but like all things I will just learn as I go.