The use of self-assembly processes, which are presided over by noncova
lent bonding interactions, has led to the construction of a variety of
mechanically-entwined and interlocked entities - namely, the so-calle
d pseudorotaxanes, rotaxanes and catenanes - of nanometre size. Althou
gh these superstructures and structures are entirely unnatural in thei
r forms, they have been constructed utilising approaches akin to those
occurring in nature.