As man-made systems become more complex and autonomous, there is a growing need for novel engineering methods that offer self-construction, adaptation to the environment, and self-repair. In a step towards developing such methods, we demonstrate how a sim- ple model multicellular organism can assemble itself by replication from a single cell, and finally express a fundamental behavior: foraging. Previous studies have employed evolu- tionary approaches to this problem. Instead, we aim at explicit design of self-constructing and -repairing systems by hierarchical specification of elementary intracellular mecha- nisms via a kind of genetic code. The interplay between individual cells and the gradually increasing self-created complexity of the local structure that surrounds them causes the se- rial unfolding of the final functional organism. The developed structure continuously feeds back to the development process, and so the system is also capable of self-repair.