To do the laser pointer activity, you'll want the following supplies:

• Laser pointer
• Paper clip or a plastic pipete with a plunger
• Tape
• Water that contains microbes

We strongly recommend parental oversight with the laser microscopes. There are enough documented cases of injuries from laser pointers that the FDA has issued warnings in the past. If you don't shine it in your eyes, you'll be fine. If you have young children in your household, be sure to keep the laser pointer out of their reach.

Any type of laser pointer will work, but a pointer with an on-switch is best because otherwise, you might have to tape down the button. Green laser pointers are usually stronger and hence a little more dangerous, so red might be preferable.

You'll also want some water with bacteria in it. You can get this from a lake or stream or from a dog dish. You can also make your own microbe-filled water by putting a small amount of baker's yeast into a cup of water. If you can get water from multiple sources, then you can compare the difference.

If you don't have the necessary supplies to make your own laser microscope, you can still watch the video to learn how the activity works. Then come back and complete it later at a better time.

Question from Lindsey81​: What’s the smallest cell?

The smallest known cell in the world is Mycoplasma gallicepticum, which is a type of bacteria that can cause respiratory disease in birds.

Photo description: Mycoplasma pneumoniae bacteria, photo credit the CDC, Paul Bradbury.

These microbes do not have a cell wall and have a diameter of only 0.2 - 0.4 microns, or micrometers. For comparison, a single human hair has a diameter equal to 70 microns. This means that it would take between 175 and 350 mycoplasmas stacked end-to-end to equal the length of a human hair!

In relation to the human body, the smallest cell is the sperm. The head, which contains the nucleus, measures about 5 microns. The largest human cell is the ova, which measures about 100 microns.