How do bees make honeycomb perfectly hexagonal?

If you look closely at honeycomb, you will see it’s made up of tiny, perfect hexagons. For over 2000 years, scholars have been trying to figure out why and how bees create such geometric perfection. And why not triangles or squares, the other two shapes which also tessellate--or fit together repeatedly without gaps? Ancient Greeks believed bees engineered this shape because it is more compact. This makes sense because wax is very expensive for bees to make. They must consume eight ounces of honey to make one ounce of wax. And mathematicians have indeed recently proven that hexagons are slightly more compact than triangles or squares. But it turns out the perfect shape is not created by the bees--at least not on purpose. It's created by simple mechanics. When researchers interrupted the bees in the middle of making honeycomb, they found that the cells started out as circles molded around the bees' bodies. As the circular cells get packed together, the heat of the bees causes the wax to melt. When the wax flattens out, the surface tension at the junctions where any three cells meet creates three perfect 120 degree angles: a hexagon. Amazingly, Charles Darwin predicted this process during his lifetime, but was never able to prove it!