Insects are diverse invertebrates within the arthropod phylum with a chitinous exoskeleton, a three-part body composed of head, thorax, and abdomen, six jointed legs, and chewing mouthparts. They constitute the most prominent animal phylum in species diversity, with over one million described. Insects can be found in almost every habitat on Earth, from polar regions to rainforests to deserts. They can also be seen from mountain ranges down to sea level, including in trees or across the ground. Some people think that insects are just pests, but they play an essential role in our ecosystem as pollinators, predators, and scavengers help maintain a balance between plants and animals.