Fig. 3. Assembly spaces.

a, Assembly observed of the three objects shown as graphs (P₁, P₂ and P₃) with their shared minimal construction process called their ‘joint assembly space’. b, Illustration of the expansion of the assembly universe, assembly possible, assembly contingent and assembly observed (see text for details). Assembly universe has no dynamics and is displayed with assembly steps as the time axis. Note that the figure illustrates their nested structure only, not the relative size of the spaces where each set is typically exponentially larger than the subset.