Welcome to the nanosize railway. Much as a train switchyard can steer rail cars to different locations, researchers have engineered protein motors to carry tiny bits of cargo to different locations.

In the body, protein motors ferry nutrients and other materials along tiny tube-shaped rails that crisscross cells. Nanotechnologists have made their own versions for years using tube-shaped rails made from DNA. Now researchers have taken that approach one step further, they report this week in Science. They’ve created DNA nanotube rails that branch in multiple directions, with each unique track made up of unique DNA patterns. Protein motors designed to recognize these patterns then carry their cargo down the desired tracks.

In the video, proteins called dyneins have been engineered to glide along DNA tracks. At a branch point, different DNA patterns of the tracks steer dyneins carrying orange fluorescent cargo to the left and dyneins carrying cyan fluorescent compounds to the right.

Nanoswitchyards should help scientists better test and understand the real thing inside cells. They may also eventually help researchers steer different drug cargoes to different tissues.