Along the side of a cockroach's body are tiny holes called spiracles. Oxygen enters the cockroach through these holes and follows the tiny breathing tubes called tracheae to all of the cockroach's body parts. Humans have skeletal systems which function to provide the structural support necessary to support their bodies. Insects are surrounded by a hard covering called an exoskeleton. This shield serves as both a structural and protective armor.
Snakes shed their skins and insects do too.
A cockroach grows inside of its old exoskeleton until the normally flat creature looks puffed up and ready to explode. Then, along its back, the exoskeleton splits and the cockroach can pull itself right out of the old crowded exoskeleton. When it does this, it is completely white and noticeably bigger. After a few hours, the new exoskeleton has hardened and now has a slightly brownish tint. After several hours, the cockroach has completely hardened and become completely brown.