Why are honeycomb cells hexagonal in shape?

Honey bees are fascinating creatures because of their incredible work ethic, sweet sugary substance and integrated social structure.
It is actually smart geometry of nature. Hexagon is the only shape which shares common boundaries with other hexagon and doesn't waste any space. Think if it was all circular small cells, there will be small gap left betwe...en them. Similarly, triangle or square can fit, but have lower surface area than hexagon. Other geometrical shapes like pentagon, heptagon, octagon will waste, space like circle.
Essentially, a hexagonal structures minimizes the surface area to volume ratio. Wax is very expensive (in terms of energy) for bees to produce. Bees have to consume 8 Oz. of honey just of produce 1 Oz. of wax. So, they would like to store as much as they can with the minimum wax possible.
Hence, the beauty is that bees are no engineers, mathematicians or architectures, still they know to create perfect geometrical shapes without any tools