Tiny but fast Frank Fox/Science Photo Library/Getty Images

Algae aren’t just scum on the top of a lake: some of the microbes can swim surprisingly fast – outpacing even the micromachines designed to one day deliver drugs inside the human body. Now comes evidence that the alga could be harnessed relatively easily for such speedy drug delivery.

Metin Sitti at the Max Planck Institute for Intelligent Systems in Germany and his colleagues figured out a way to yoke an alga like an ox and then steer it through the body using magnetic fields as the reins.

They started by attaching …