Imagine you can see the tiny bugs that crawl around in liquid all the time with a simple laser pointer. It will cost you less than 20bucks to do it. Sound interesting? Try it out.
Step 1: Get a Green Laser Pointer
First of all you will need a green laser pointer. It does not need to be powerful. A simple laser like the ones you play with your cat is fine. At this point I am using a 30mW green laser pointer
Step 2: Prepare a Drop of Water
Apply few drops of filthy water on a metal wire. please make sure the water is in droplet form. The water can't be clean either. You'll have to visit a pond or grab some from a puddle in a field.
Step 3: Shining the Laser on the Water Drop
Project the laser to the rounded end of the water drop, a projection of the light should formed on the wall behind the drop.
Step 4: Observe the Image
From the projection on the wall, it shows blurry pictures of the critters inside the droplet. These distorted light waves interfere with the incoming light, and so there are areas of extreme light and extreme shadow, which shows us the contours of the microscopic organism.