Blood!

Just for fun I setup our highest-spec microscope and had a look at a sample of my own blood. The scope was a Zeiss Axiovert 200 inverted microscope with a 100x oil-immersion objective (NA=1.2) and oil immersion condenser (NA=1.4, stopped down to 0.8). An additional "tube-mag" of 1.5x was applied and the eyepieces yielded an extra 10x. The total optical magnification between sample and eyes, then, was 1500x. Notice the 10 micron scale line in the top-left corner of the image.

I love this microscope. It can yield great images, if you spend a little time setting it up. In fact its performance is on the edge of what is theoretically possible with conventional light microscopy.

Hi-res version here