How do you mend a broken heart? You’re operating on a heart and it’s got a tear in it. How do you seal it?

Sutures? Staples? These are the traditional answers, but they aren’t good ones. Both involve piercing tissue and creating holes, which is bad news for an organ that’s constantly moving, and vigorously pumping blood. Holes lead to clots. They also bleed.

And if you specialise in doing heart surgeries on babies, as Pedro del Nido from Boston Children’s Hospital does, you can add small size and delicate tissues to those other challenges. “The holy grail for heart surgeons, especially for those who work on babies, is to attach things without damaging the normal underlying tissue,” he says.

A glue,