a quantitative agreement with experiment. Today the model is called free electron model (FEMO). He saw the reason why he had failed in polyenes: an instability when assuming equal bonds leads to an alternation between single- and double-bonds caused by the condition of self-consistency between bond length and π-electron density distribution. He justified this assumption by finding agreement between measured and theoretically predicted absorption spectra. Later this assumption was theoretically verified. This effect is often called Peierls instability: starting from a linear chain of equally spaced atoms Peierls considered first order perturbation theory with Bloch functions showing the instability, but he did not consider the self-consistency resulting in the transition to alternation of single and double bonds. The particular properties of conducting polymers are based on the theoretical relation between bond alternation and equalization. The FEMO and its improvements led to a theory on the light absorption of organic dyes.<ref name=Zech>H. Kuhn: The Electron Gas Theory of the Color of Natural and Artificial Dyes'. Progress in the Chemistry of Organic Natural Products (L.Zechmeister ed.) 16:169 (1958) and ibid. 17:404 (1959).</ref> In Marburg, shortly before the age of digital computers, Kuhn and Fritz Peter Schäfer developed an analogue computer to solve the 2-dimensional Schrödinger equation. This room-filling analogue computer was applied by Kuhn's research group to calculate bond lengths in π-electron systems.H. Kuhn: Analogiebetrachtungen und Analogrechner zur quantenmechanischen Behandlung der Lichtabsorption der Farbstoffe Chimia 15:53-62 (1961)H.D. Försterling, W. Huber and H. Kuhn: Projected electron density method of π-electron systems I. Electron distribution in the ground state. Int. J. Quantum Chem. 1, 225 (1967). In the beginning of the 1960s, Kuhn thought about a new paradigm in chemistry: the synthesis of different molecules which fit structurally into each other in such a way that they form planned functional units (supramolecular machines). His research group constructed simple prototypes of supramolecular functional units by advancements of the Langmuir–Blodgett films.H. Kuhn, D. Möbius: "Systems of monomolecular layers-assembling and physico-chemical properties" Angew. Chem. Int. Ed. Engl, 10:620–37 (1971). Such films are known today under the name Langmuir–Blodgett-Kuhn-films (LBK-films) or Langmuir–Blodgett-Kuhn-(LBK)-layers. The many different techniques to manipulate systems of monolayers were developed in close cooperation of Kuhn and Dietmar Möbius. Thus the layers should be called Langmuir–Blodgett-Möbius-Kuhn (LBMK)-layers. In close correspondence to the objective of constructing supramolecular functional units he (now at the Max Planck Institute for Biophysical Chemistry in Göttingen) approached theoretically the origin of life: