A 2-dimensional foam of wet soap bubbles squashed between glass plates, after 10 hours of coarsening by the diffusion of gas from smaller to larger bubbles. The green curves are circular arcs, fit to the Plateau borders that connect adjacent three-fold vertices; the red curves represent uncertainty in their curvature. For scale, each Plateau border is 1/3 mm across.
Image Anthony Chieco, Doug Durian
Beautiful Science page