Fig. 2.

Increasing complexity of extracellular environments through hydrogels. Hydrogels can be engineered to recapitulate aspects of extracellular environments. For example, they can be designed to display cell-cell (A) and cell-ECM (B) moieties. In addition, hydrogels may present various 2D uniform (left), gradient (middle) or patterned (right) molecular cues to guide cellular behaviors (C) or pseudo 3D topologies such as microgrooves (left), fibrous structures (middle) or through folding or buckling of 2D substrates (right panel) (D).