The answer to the question in this context is a particular chicken protein.

But there is a further twist as this particular chicken protein turns out to come both first and last.

That neat trick it performs provides new insights into control of crystal growth which is key to eggshell production.

Researchers used a powerful computing technique called metadynamics in conjunction with the UK National Supercomputer in Edinburgh to crack this egg problem.

"Metadynamics extends conventional molecular dynamics (MD) simulations and is particularly good at sampling transitions between disordered and ordered states of matter," said Dr David Quigley of the Department of Physics and Centre for Scientific Computing at the University of Warwick.

Dr Quigley and his colleagues created simulations that showed exactly how the protein bound to amorphous calcium carbonate surface using two clusters of arginine residues, located on two loops of the protein and creating a chemical 'clamp' to nanoparticles of calcium carbonate.

While clamped in this way, the OC-17 encourages the nanoparticles of calcium carbonate to transform into calcite crystallites that form the tiny of nucleus of crystals that can continue to grow on their own.

But they also noticed that this chemical clamp didn’t always work.

The OC-17 just seemed to detach or 'desorbe' from the nanoparticle.

"With the larger nanoparticles we examined we found that the binding sites for this chemical clamp were the same as the smaller nanoparticles but the binding was much weaker," said Professor Mark Rodger of the Department of Chemistry and Centre for Scientific Computing at the University of Warwick.

"In the simulations we performed, the protein never desorbed from the smaller nanoparticle, but always fell off or desorbed from the larger one."

"However in each case, desorption occurred at or after nucleation of calcite."

This elegant process allowing highly efficient recycling of the OC-17 protein.

Effectively it acts as a catalyst, clamping on to calcium carbonate particles to kick-start crystal formation and then dropping off when the crystal nucleus is sufficiently large to grow under its own steam.

This frees up the OC-17 to promote more yet more crystallisation, facilitating the overnight creation of an eggshell.

It is hoped that this new insight will be of great benefit to anyone exploring how to promote and control artificial forms of crystallisation.