A pesticide is a chemical that is used to kill or prevent small animals (or organisms) which are considered to be unwanted. These organisms are called pests. Some of these pests that people do not want are insects, microbes that destroy plants, and other things that affect humans in a bad way and it may kill humans too. Many pesticides are poisonous, and are bad for not only the organisms they kill, but for humans too. A pesticide also affects the environment