The blue whale is the largest animal that has ever lived in our planet's history, bigger than the biggest dinosaurs.
Baleen whales have huge mouths but small gullets, and they feed on small things.
Baleen whales feed by straining their food through baleen, which is a massive sieve-like structure hanging down from the upper jaw. Toothed whales are mostly smaller than the baleen whales. The toothed whales include all the dolphins, porpoises, killer whales etc, as well as a jsterious group called the beaked whales. They all have teeth, but the number varies widely. They eat lots of different things, ranging from squid to many kinds of fish.