Knots are generally understood to form due to twists and turns of long, flexible materials that keep shoes on your feet or frustrate your attempts at hanging holiday decorations. A beam of light doesn’t sound like a material that can create a knot.

But it is.

Imagine throwing several rocks into a pond all at once. At a certain point on the water’s surface, the resulting ripple rings would all mix to form a complex pattern. Now imagine being able to control the shape and speed of each ring. With enough planning, you could get that mesh point to form complex shapes in 3D on demand.