Each year, bouts of norovirus — a stomach bug — cause misery in 19 to 21 million Americans. Scientists at last are homing in on how this nasty virus does its work. 

When researchers tattooed mouse tails, the only cells found with ink inside were immune cells. The tattoo appeared the same before (above) and after (below) these ink-holding cells had been killed. Why? New immune cells recaptured the ink.

Dickinsonia was one of the first animals on Earth. It lived on the ocean floor 550 million to 560 million years ago. It looked like a giant version of the modern-day Trichoplax, the simplest animal now alive.

Here’s a tropical “research assistant” belonging to the genus Haemadipsa.