Smoke rings are being seen in a new light. Doughnut-shaped structures called vortex rings are sometimes seen swirling through fluids. Smokers can form them with their mouths, volcanoes can spit them ...

A complex maze of lasers, lenses and mirrors has been used to twist light into a vortex shaped like a doughnut. Vortex rings are common in fluids – think of smoke rings floating in air or underwater ...