Shells were first used by the Creator of the earth and its inhabitants. The list of natural shell-like structures is long, and the strength properties of some of them are remarkable. Egg shells range in size from those of the smallest insects to the large ostrich eggs, and cellular structures are the building blocks for both plants and animals. Bamboo is basically a thin-walled cylindrical structure, as is the root section of a bird's feather. The latter structural element develops remarkable load-carrying abilities.

The degeneration of a bifurcation point into a limit point due to presence of imperfections … suggests that bifurcation is an exception rather than the rule. In spite of this the literature on elastic stability and buckling of structures deals preponderantly with bifurcation buckling problems. Human frailty is, perhaps, the main reason for this state of affairs.