We now compare the results of the threshold sampling to the output from CSP on tetrolic acid, in this case restricting CSP to the space groups of the two known polymorphs (P 1 and P 2 1 ). The resulting structures are shown in Figure in the representation often used in CSP studies: plotting the energy vs density of all predicted structures. Structures sampled during threshold searches are also shown and labelled by whether they belong to the funnels around α, β or are disconnected from those superbasins at a lid energy 40 kJ mol -1 above α. A first observation is that crystal structures in the α and β funnels occupy overlapping regions of energy-density space, so that the traditional CSP representation does not convey the important information about which structures belong to connected regions of the highdimensional energy landscape. The disconnectivity graph conveys this information more clearly.