Embryonic development of the nematode C. elegans has been considered to be mosaic. Before the publication of this paper, differentiation of cells, including those of the gut, was thought to be cell-autonomous, so that cell-cell interactions were not required. The single author of the paper, as a graduate student, showed that the fate of the gut is actually induced by cell-cell interaction. I will discuss what caveats existed in previous experiments and how he changed the widely accepted view. I will also discuss how the interpretation of the results of the paper had changed through subsequent experiments.