The objectives of materials science are considered in context with complete cycles of materials. The matter passes through the following stages: primary raw material from deposits (alpha), production of engineering materials (W), fabrication of systems (F) their use (G), their failure (V), and recycling or redepositing (Omega). The changes of energy and entropy are discussed which occur during this sequence principally due to separation, mixing and ordering of atoms. A characteristic feature of modern technology is a reduced amount of material required for a certain useful function (due to improved material properties), while the complexity of technical systems is increasing. Consequently, the individual cycles of a large number of materials are combined in a system for the duration of its use. This leads to efficient machines, but also to complex mixtures of matter at the end of its use, i.e, to an increase of entropy. After a material has done its duty efficiently, safely, and for a long period of time, it finally will become scrap. There exist several options for its further fate. They depend on the microstructure of the material, on fabrication, design and failure of the machine. Most favourable is the closure of a cycle by regaining secondary raw materials (Omega --> alpha) or secondary engineering materials (Omega --> W), - least fortunate is a fine dispersion of a dilute mixture of atoms on the solid surface of the earth, in water or in the atmosphere. Intermediate is concentrated dumping in secondary deposits or regaining of stored energy by combustion. Cycles can be closed rather easily with established materials based on iron, or even better with light metals (Al, Mg). The same is true for well-classified ceramic glasses and thermo-plastic polymers. A closure of cycles is also possible by acquiring carbon from CO2 via biosynthesis of natural polymers (starch, cellulosis). It will be a rewarding task to future materials science to provide the fundamentals for aiding the development of ''recycling-friendly'' materials, fabrication, and design methods. Materials science should also help to create a more rational discussion of the best choices for materials selection and recycling methods.
