Arthropods' rigid exoskeletons provide protection and the basic building material for an arsenal of tool-like appendages. But the exoskeleton also has its downside. Since the exoskeleton is hard and its outer layer is non-living, it cannot grow bigger by small increments as the human skeleton does. Instead, arthropods must go through the delicate process of shedding the old exoskeleton and expanding to a larger size before the new exoskeleton hardens. This process is known as molting.
