This chapter is a survey of the similar genetic mechanisms used by humans and flies to establish the major axes of their bodies. In both cases the anterior-posterior axis is regionalized by the same set of clustered Hox genes that have been inherited from their common ancestor. The dorsal-ventral axis is also organized by conserved genes (BMP and Chordin), which in this case encode morphogens. Morphogens are diffusible proteins whose concentration allows cells to determine their location along the morphogen's concentration gradient. The third (left-right) axis does not actually use any morphogens in the strict sense of the word, and the way that it is created differs in humans vs. flies. Much of this chapter is a historical review of the major discoveries in evo-devo pertaining to body axes. That history is full of ironies which have misled us to make incorrect assumptions about what features are conserved and which ones are convergent. A concerted effort is made to tease fact from fiction, based on the most extensive data set we currently have about gene expression in animal phyla. One key topics is segmentation, and the controversies concerning its origin are reassessed.