The article discusses a research being done on wingless gradient. It references a study by E. Piddini and J. P. Vincent in the 2009 issue of "Cell." It notes that the study by Piddini and Vincent reveals that in Drosophila melanogaster, the wingless (Wg) morphogen does more than just trigger gene expression. It mentions that the authors used models to look at the expression of Wg target genes.