The "vernier" mechanism is one of only a
very few ways (Figure 1) proposed for regulating the size of the resulting aggregate, but no
instance of a vernier's operation has yet been demonstrated in either a biological or nonbiological
setting. The first example of a molecular vernier is now described (Figures 2 and 3): Three
molecules of a dicarboxylate combine with two molecules of a triguanidinium to give a pentamer
of predetermined dimension.