13 Vector Equilibrium Spheres Fractal - small

12 cubeoctahedral spheres surround the central sphere. The centres of the spheres are the same distance from their neighbors as they are from the centre of the central sphere.  The cubeoctahedron is the only shape in 3d that does this, and for this reason Buckminster Fuller called it the Vector Equilibrium.

A slightly larger version is available here

This demonstrates  the natural way that spheres cluster. In the same way that 6 circles perfectly surround a central circle 12 spheres surround a central sphere. It is the most basic example of the tetrahedral symmetry of space itself and when this pattern is extended Fuller called it the Isotropic Vector Matrix.

Because it is the closest sphere packing it is the way that cells will naturally cluster. It is the path of least resistance for energy within form.