One Petri dish per hand containing universal culture medium (e.g., contact plates, available from laboratory supply stores or pharmacies). Permanent marker, adhesive tape, scissors, water, soap.

Label the Petri dish with your name and the date. Divide the Petri dish into two halves, one for the washed finger and one for the unwashed finger. This is important for matching the two fingerprints later.

Gently press your unwashed finger onto the correct half of the culture medium for two to three seconds. Then close the Petri dish. Wash your hands thoroughly with soap. Repeat the fingerprinting on the other half of the culture medium. Close the Petri dish with the lid and seal the rim with adhesive tape (do not open the dish again). Now you need to store the Petri dish in a warm place (not too hot, not in direct sunlight) at least overnight. You may not see results immediately the next day; this can take three to four days.

a) Look closely at both sides of the bowl. What can you see? ________________________________________________________________________________________________________________________________________________________________________________________________________________ b) Do both sides look the same, or can you see a difference? ________________________________________________________________________________________________________________________________________________________________________________________________________________