These invertebrates have long thin bodies made of many segments, protected by an exoskeleton. Each segment has two pairs of legs. They have a pair of antennae on their head, and chewing mouthparts. Most have glands along their body that make toxic compounds to discourage predators. Most millipedes are darkly colored, but some very toxic ones are bright.
Millipedes are found all over the world, and are most diverse in the humid tropical regions.
Millipedes live on land, but they need to live in moist places, and most live in forested areas (though there are plenty in grasslands and other habitats too)
Millipedes don't change their structure much as they grow. Babies look like small adults. As they grow they shed their exoskeleton to make more room.
Millipedes are not usually social. They become active when it is not to bright or dry.
Millipedes have very poor vision. They probably communicate with touch and smell. A few species glow in the dark, probably to warn predators that they are poisonous.
Millipedes eat dead plant material. They have bacteria and other microbes in their digestive system that helps them break down the dead leaves and other foods they eat. They sometimes eat the dung of herbivores.
Millipedes can't run fast, so they have protection. They curl up to protect their legs, and they give off toxic chemicals to poison their predators or at least taste bad.
Millipedes can be important decomposers, especially in tropical forests.