The woolly mammoth was originally a tropical creature, but because of its special hemoglobin it could adapt to much colder regions. The hemoglobin was reconstructed by Kevin L. Campbell of the University of Manitoba, this was a mammoth-sized task. They gathered DNA from the mammoth and looked at its closest living relative's DNA, the Asian elephant. They were merged together, and then two strands of globin from each were injected into living bacteria. This irritated the bacteria and formed iron, which is a "key ingredient" in red blood cells. Currently Campbell and his team are doing more tests to the mammoth bones.
This is extremely neat, science has come so far. First we are cloning sheep, and now we are recreating (from scratch) blood for a woolly mammoth. Just imagine if they actually succeed in recreating a mammoth. The giant beasts of the tropics and ice would roam the Earth once again. It may not be in our lifetime, but for the future generations wouldn't that be neat? But if they don't succeed in making one, they have come far enough to make it's blood, which is still very cool.