Lizards come in many shapes and sizes; the smallest is a few centimeters going to the biggest at about 9 feet or more. Among the 3,000 species of lizards only two - the Gila monster and the Mexican beaded lizard are poisonous. The largest lizard in the world is the Komodo dragon. These 10-foot long lizards have the ability to bring down animals bigger than they are. Their saliva is also toxic. Geckos are the only lizard that has vocal cords, and the ability to use them. Other lizard species use body language, such as gestures, for communication. Most lizards have amazing eyesight. Many lizards even have color vision. Some lizards, such as the chameleon, can change the color of their skin to blend into their surroundings. They use this as a form of protection.