Each player controls the growth and expansion of a strain of bacterium within the confines of a petri dish. The goal is to become the dominant strain.

Each player starts with a single germ. Germs may grow and divide to produce more germs, which may grow and divide to produce more germs, etc. Germs may also move, and they may attempt to surround opposing germs. When a germ is surrounded, it dies.

The petri dish contains 4 goal areas. The first player to gain exclusive control of 3 of the 4 areas, wins.

The game consists of a board (representing the petri dish), 16 red and 16 blue 7/8" poker chips (the germs), 2 pages of rules, and 2 reference/illustration cards.