In this paper, strategies for controlling pattern formation in Caenorhabditis elegans are reviewed. The somatic tissues of this small nematode develop, in large part, by invariant cell lineages, whereas the germ-line tissue arises primarily by a variable pattern of divisions. The spatial organization of the germ-line tissue depends on special regulatory cells, the distal tip cells, which appear to influence nearby germ cells to remain in mitosis. In somatic tissues, the problem of specifying that a cell in a particular position assumes a particular fate seems to be controlled by a number of different strategies. These include the production of non-equivalent cells in particular positions of the lineage tree, local interactions between apparently equivalent cells in close contact, and the influence of another special regulatory cell, the anchor cell, over certain neighbouring cells.