Model surfaces presenting gradient arrays of ligands have been used for the first time to study tissue shape morphing and directed tissue migration (J. Am. Chem. Soc., DOI: 10.1021/ja204893w). The study details a strategy for preparing biologically active and chemically selective substrates for investigating various cellular processes including adhesion, migration, and differentiation. Wei Luo and Muhammad N. Yousaf of the University of North Carolina, Chapel Hill, used microcontact printing to form a pattern of hydrophobic regions on gold to which they attached fibroblast cells. In the other regions, they deposited hydroquinone-capped molecules, which, after photo- and electrochemical treatments, were functionalized via oxyamine linkages with RGD, a tripeptide that promotes cell migration and adhesion. By controlling the size, shape, and concentration gradient of the RGD regions with patterned photomasks, the team caused cells and tissues to migrate to the RGD regions and form new patterns. In addition, they measured the rate of directed tissue morphing and its dependence on the slope and direction of the gradient.