An examinaton of the human body as an environment for the billions of tiny organisms living within it. Includes film footage of: underwater life - crab, octopus, eel; amoeba; human cells; blood circulation; breathing; digestion (animated simulation); white corpuscles; tapeworm organism; fungus; skin lice; malarial organism; skin bacteria; plague bacteria; cholera organism; flu and polio virus; white corpuscles; antibodies; and penicillin attacking alien organisms in the human body.