The article discusses the development and application of biomaterials in controlling stem-cell fate, both in vitro and in vivo. Biomaterials are being designed to mimic the complex microenvironments of stem-cell niches, which are crucial for maintaining stem-cell identity and promoting their differentiation. The authors highlight the importance of understanding the biochemical and biophysical cues that regulate stem-cell behavior, such as the stiffness of the extracellular matrix (ECM) and the spatial arrangement of ECM components. They also emphasize the use of advanced technologies like microfabrication and microfluidics to create versatile model systems for studying stem-cell biology. The article outlines specific examples of how biomaterials can be used to control stem-cell fate, including the use of hydrogels, ECM arrays, and microfluidic platforms. Additionally, it explores the potential of biomaterials in delivering stem cells and niche signals in vivo, as well as the challenges and future directions in this field. The authors conclude by emphasizing the need for interdisciplinary collaboration between cell biologists and materials scientists to advance stem-cell research and its clinical applications.The article discusses the development and application of biomaterials in controlling stem-cell fate, both in vitro and in vivo. Biomaterials are being designed to mimic the complex microenvironments of stem-cell niches, which are crucial for maintaining stem-cell identity and promoting their differentiation. The authors highlight the importance of understanding the biochemical and biophysical cues that regulate stem-cell behavior, such as the stiffness of the extracellular matrix (ECM) and the spatial arrangement of ECM components. They also emphasize the use of advanced technologies like microfabrication and microfluidics to create versatile model systems for studying stem-cell biology. The article outlines specific examples of how biomaterials can be used to control stem-cell fate, including the use of hydrogels, ECM arrays, and microfluidic platforms. Additionally, it explores the potential of biomaterials in delivering stem cells and niche signals in vivo, as well as the challenges and future directions in this field. The authors conclude by emphasizing the need for interdisciplinary collaboration between cell biologists and materials scientists to advance stem-cell research and its clinical applications.