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Oxygen is the third most abundant element in the universe and makes up one-fifth of the earth's atmosphere. Any change in this proportion - either up or down - would threaten humankind. It is highly reactive and is able to corrode metals and destroy natural organisms. Oxygen is thus regarded both as the stuff of life and as a hastener of ageing.

For such a vital element, its discovery proved surprisingly elusive. Even now, there are rival tales about who really discovered it.

Do you know what colour oxygen is? Or how to get it into liquid form, considering it boils at -183C? Watch our video to see Dr Andrea Sella giving us the lowdown on this incredible element, vital for life on Earth.

Read the transcript of this video (PDF, 53KB).