Microarray expression profiling for identification of Hox downstream targets. (a) Hueber et al.  compared Drosophila embryos overexpressing a control lacZ gene (blue) with embryos individually overexpressing various Hox genes (yellow). (b) Hersh et al.  searched for targets of Ultrabithorax (green) in haltere imaginal discs by comparing their transcriptome with that of wing imaginal discs (gray).