Big snail shell
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Calcium: Nature's building material

Nature uses calcium to build wonderful structures - from spiral shells to the human skeleton - and now, so do we humans.

Presenter Justin Rowlatt goes to the Royal Institution in London, where our favourite chemist, Andrea Sella, describes the explosive chemistry with which Sir Humphry Davy first isolated this element two centuries ago.

Justin visits the Aspdin kiln - a strangely overlooked historic relic that is arguably the birthplace of a global industry that consumes vast quantities of calcium.

And we peer into an enormous hole, right in the heart of London, part of the biggest construction project in Europe - Crossrail.