 cryptic sites are short signaling peptids embedded within the extracellular matrix, ECM, which can be activated by enzymes to trigger cellular responses. By mimicking this process, researchers have developed synthetic ECM hydrogels that can respond dynamically to external stimuli such as enzymes or cells. These hydrogels contain switch peptids that can rearrange their primary sequence upon exposure to specific enzymes, resulting in the formation of pentapeptides that exhibit increased bioactivity. The presence of these pentapeptides allows for the development of a dynamic reciprocal relationship between cells and the ECM, allowing for the controlled release of bioactive molecules from the hydrogel. This article was authored by Yuman Chu, Yulia Shmitov, Elizabeth A. Harris, and others.