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The skeleton of this glass sponge is made of tiny 'spicules' of silica. When you carefully examine the cross-section of a spicule, you'll see it's made of concentric layers. This helps stops cracks from growing through the spicule! And the variable thickness of these concentric layers turns out to be optimized, to make them as strong as possible.

Even though we know this now, we would still be unable to create a machine that grows its own skeleton of silica, made of optimized spicules. So there's a lot left to learn!

For a prettier picture of this glass sponge, read on....

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