The extracellular matrix (ECM) presents a complex myriad of biochemical and physical cues in the stem cell niche and is able to modulate stem cell fate and function. This review summarizes engineering approaches that have exploited natural and synthetic biomaterials to understand ECM regulation of stem cell fate. Specifically, we demonstrate how these studies have advanced our understanding of vascular maturation and mesenchymal lineage specification. ECM mechanics have emerged as a critical cue in stem cell lineage specification. With the introduction of mechanically dynamic materials, which mirror the non-linear elastic behavior of natural matrices, our understanding of differentiation behavior has evolved. While studies using conventional culture employing rigid, two-dimensional surfaces have greatly advanced our understanding of stem cell differentiation, they overlook the complexity of ECM in the stem cell environment. Implementing defined analogs, through material science and tissue engineering approaches, will allow us to mirror the dynamic nature of ECM and fully elucidate how stem cells differentiate.