The ubiquity of the prefix ‘nano’ (Greek: dwarf) in conjunction with metre, scale, structure, fabrication etc in present day (serious and not so serious) scientific and technical literature is startling. Clearly, this signals a great amount of activity in a field that one could quite generally call ‘engineering materials on the atomic scale’. To appreciate the length scales involved, one recalls that one nanometre, abbreviated as 1 nm, equals 10−9 m or one millionth of 1 mm. The atomic scale can be visualized by measuring the size of a cobalt atom in a piece of cobalt metal. If we put one of these atoms in a sphere we arrive at a radius of about 0.14 nm. Imagine that we place a number of cobalt (Co) atoms side by side like a necklace of pearls, in this way obtaining a monatomic Co chain. Can this be done in reality? Can the physical properties of such chains (or wires) be determined? The answer to these questions is quite remarkably yes. In an attempt to assemble a necklace, one first needs a flat surface to align the pearls. The same is true for the atomic engineer who, one should hasten to say, actually is a physicist; in the experiment of interest here,Gambardella and colleagues [1–3] used the surface of platinum (Pt) oriented in such away that it consists of flat portions separated by regularly spaced steps, not unlike a staircase. Cobalt is brought onto the surface in tiny amounts by evaporation. In a certain temperature range the atoms glide about the surface like ice-skaters getting stuck at the edges because there the binding energy is larger than on the flat portions. This fabrication process, an art in itself [4], results in a very large number of regularly spaced straight Co chains glued to the edges of the Pt steps. Indeed, we can really see all this with the scanning tunnelling microscope (STM). In 1981 this instrument was invented by Binnig and Rohrer (Nobel prize in 1986); it actually initiated the substantial progress in surface physics and the fabrication of nanostructures on surfaces. A picture of the steps and Co chains can be seen in figure 3 of Gambardella’s paper [3]. A modern, very promising development of the STM is described in this Special Issue [5]. Turning now to the physical properties of the Co chains we briefly recall the phenomenon of magnetism. In various forms and guises,magnets are encountered in daily life. The compass needle is the best known example—an old one, too; much more frequently you perhaps notice the magnetic strip on your credit or bank card. Various electric motors and the starter in the automobile employ permanent magnets. Your PC’s storage unit is a delicately fabricated magnetic device, where modern surface physics is being used in the magnetoresistive reading head. At the basis of these metallic magnets are generally iron, cobalt, nickel and some