In Chapter 2, we learned that biological systems have elaborate designs that cannot be matched by conventional engineering, thanks to the various self-organizing mechanisms deployed in each layer of their hierarchy. In Chapter 3, we summarized several attempts to reconstruct such biological mechanisms artificially. If we can uncover the principles of these mechanisms through reconstruction efforts, then we can in turn apply these principles in making devices for our own purposes. In other words, we proceed from science to engineering. Even if we obtain ideas for basic notions and principles from biological systems, though, when we actually build devices, many practical issues remain to be resolved. In such specific problem solving stages, there is no need to look to nature for ideas anymore; although humans were inspired by birds to create flying machines, the actual airplanes constructed by humans have quite different structures from those of birds. The technology or materials currently at hand must be used, and the problems may be solved with new ideas. The aim of this chapter is to construct artificial systems like the ones we discussed in Chapter 3, but this time from an engineering perspective. Specifically, we consider how to make systems which have self-assembly and self-repair functions.