1. Melt 15 milliliters of agar mixture in a microwave (about one minute on high)in the smaller container. Let cool until warm to the touch.
2. Add the bacteria and antibiotics (if you have them). Mix vigorously, but do not create bubbles.
3. Pour the mixture into a petri dish and quickly cover with a lid. Let it cool until solid, about 20 minutes.
4. Remove the lid, cover the petri dish with plastic wrap, and cut three narrow slits in the plastic.
5. Tape the transparency to the bottom of the petri dish, flip it over, and shine red light down onto the transparency for one to three days. (Make sure the light doesn't melt the agar, as this will kill the bacteria.)
6. Admire your work. The petri-dish photograph can last for several years in a refrigerator.