12 cubeoctahedral spheres surround an empty space that would fit a 13th sphere. Therefore this form is made of 12 smaller versions of itself. Another version with the 13th sphere present is available
here
It shows the primary geometric and energetic symmetries of space.
Buckminster Fuller called this form created by the centre of the 12 spheres the 'Vector Equilibrium'. He described it as the still point from which all movement emerges.
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 has this property.
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.