Penguins keep warm in freezing temperatures through a few different mechanisms. One way is their dense layer of feathers, which provides insulation and helps retain body heat. Additionally, penguins have a layer of fat under their skin that acts as a source of insulation. They also have a unique blood circulation system that allows them to regulate blood flow to their extremities, conserving heat and keeping their core warm. Lastly, huddling together in groups helps penguins generate and maintain body heat collectively.