Vlatko Vedral, Co-=Direct oof the Oxford Martin Programme on Bio-Inspired Quantum Technologies, gives a talk for theOxford Martin School. Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles. Nearly all physicists, though, think it applies to everything, no matter what the size. The reason its distinctive features tend to be hidden is not a simple matter of scale. Over the past few years experimentalists have seen quantum effects in a growing number of macroscopic systems. The quintessential quantum effect, entanglement, can even occur in large systems as well as warm ones - including living organisms - even though molecular jiggling might be expected to disrupt entanglement.