data molecular processing requires assemblies of molecules or supermolecules designed for exhibiting specific properties. three methods make it possible to meet this requirement' bio-engineering methods for the synthesis of artificial proteins of enzymes which induce the right organization in the molecular edifice. although this method is very promising, the present knowledge in proteinology is still too poor to predict the structure of artificial proteins the synthesis of supermolecules containing all the required active groups held in the right geometry by convenient links and spacers some recent spectacular results have shown the method to give rise to efficient supermolecules. the main problem is the large amount of chemical synthesis before experiment can take place. the langmuir-blodgett method which makes use of physical forces to hold together small molecules easy to synthesize. the lb method affords several variants and a specific chemistry which allow the building and the in situ modification of molecular assemblies to give them the required properties. several examples illustrate the ease of fabrication of tailored molecular assemblies. even highly sophisticated structures like the molecular cell automaton can be reasonably looked to by this method, which is now well controlled the stability of the molecular assemblies in adverse conditions seems to be its main limit' the lb method shows up as a fast, efficient tool for a first approach to tailored molecular assemblies stable enough to be studied and sorted out. but no one can predict what the final form of the