Breeding Bacteria & Growing Microorganisms: For this activity, you will need agar. Agar can be purchased at some vitamin/health food stores or online. How to: 1. Prepare your petrie dish of agar. 2. Using a cotton bud to swab a certain area of your house 3. Rub the swab over the agar with a few gentle strokes 4. Place the lid on the Petrie dish 5.Let the dish to sit in a warm area for 2 or 3 days 6. Check the growth of the bacteria each day 7. Dispose of the bacteria without opening it up!