In order to survive, animals must be able to sense what is happening in the environment. Some animals have excellent sight, others a great sense of smell or taste. The senses are used to find food, mates, to avoid toxins and predators. The small worm C. elegans has a set of sensory neurons that detect various conditions in its environment, almost like a sense of smell. It is an ideal organism for studying how animals interact with their environment because its sensing systems and reactions are simple and can be understood at a genetic level.