Why are blue whales so enormous?

Blue whales are the largest animals on the planet, but what helps them grow to the length of a basketball court? Asha de Vos explains why the size of krill make them the ideal food for the blue whale -- it's as if the blue whale was made to eat krill (and krill was made to be eaten by the blue whale). [Directed by Cognitive Media, narrated by Asha de Vos].