Researchers have developed a photosensitive hydrogel that could aid the development of high-resolution 3-D cell microenvironments for engineering tissues, growing miniorgans, modeling diseases, and screening drug candidates. Scientists have made cell microenvironments primarily from two substances: collagen gels, which are natural protein-based systems that are not readily customizable, and polyethylene glycol, which is not photosensitive and therefore not tunable at subcellular resolution. Now, Xiao-Hua Qin of Empa, the Swiss Federal Laboratories for Materials Science & Technology, and coworkers have developed a high-resolution, light-induced technique for forming polyvinyl alcohol cell matrices (Adv. Mater. 2018, DOI: 10.1002/adma.201705564). After generating a polyvinyl alcohol norbornene hydrogel, the team applies a direct laser-writing technique called near-infrared multiphoton lithography and a cross-linking reagent to forge dicysteine-peptide connections between the strands in the gel (shown). The resulting microenvironments are customizable at micrometer spatial resolution, and the peptide linkers are protease sensitive, allowing cells to restructure the matrix to make additional space for cell migration when needed. “This system will enable biologists to study and manipulate multicellular microenvironments on demand to better understand tissue development and diseases,” the researchers note.