Cats knead with their paws for a variety of reasons. Kneading is thought to be a way for cats to show contentment, as it is often accompanied by purring. Additionally, kneading is believed to be a way for cats to mark their territory, as they may leave their scent behind on objects they knead. Finally, kneading is also thought to be a way for cats to stimulate the production of milk when they are nursing their young.