Mechanical forces significantly influence stem cell behavior during development and regeneration. Stem cells and their microenvironment communicate through mechanical cues to regulate cell fate, behavior, and developmental processes. During embryonic development, mechanical forces pattern tissues and organs, while in adult tissues, mechanical interactions with the extracellular matrix (ECM) maintain stem cell potency. In vitro, synthetic stem cell niches can precisely control biophysical and biochemical properties to study how mechanical cues, such as matrix stiffness or applied forces, direct stem cell differentiation and function. Understanding stem cell mechanobiology informs the design of artificial niches for regenerative therapies. Mechanical cues guide development by influencing cell-cell adhesion, tissue morphogenesis, and stem cell fate. Intrinsic and extrinsic forces drive early embryo development, with contractile mechanical cues enabling self-organization and germ layer specification. Intrinsic forces, such as those generated by actomyosin complexes, regulate embryonic morphogenesis, including axis elongation and gastrulation. Extrinsic forces, like fluid shear, also influence development by signaling through primary cilia and generating morphogen gradients. Cell-ECM interactions guide later development, with ECM stiffness and composition affecting stem cell behavior. Mechanical forces regulate organogenesis by directing progenitor cells to specialized functions. For example, mechanical forces in the developing lung support smooth muscle development, while shear forces in the heart promote hematopoiesis and cardiac morphogenesis. Mechanical cues also influence multi-scale developmental processes by connecting macro-scale physical inputs with nano-scale molecular signals. Complex patterning depends on cell-ECM interactions, with physical traction forces on the ECM promoting the formation of organized structures. The mechanical properties of the ECM regulate mammary gland morphogenesis and angiogenesis, with matrix stiffness affecting biochemical signals and cell fate. The study of mechanobiology is complex due to the influence of mechanical stimuli on multiple aspects of cell behavior, including matrix traction forces, membrane curvature, and cell fate. Synthetic niches with tunable mechanics are used to study how mechanical cues regulate stem cell behavior. These systems allow independent control of mechanical, matrix, and soluble cues, enabling the investigation of how mechanical properties influence stem cell mechanobiology. 3D systems provide more accurate mimicry of in vivo environments, with mechanical properties and diffusion affecting stem cell behavior. Alginate systems are suitable for studying how physical parameters influence stem cell mechanobiology, as they allow independent regulation of crosslink density, stiffness, and viscoelasticity. Extrinsic forces can be applied to stem cells in bulk or microscale systems to directly probe mechanoresponses. These forces, such as cyclic strain or hydrostatic pressure, influence stem cell behavior and can be combined with micro-scale measurement techniques to study mechanotransduction. Mechanical cues regulate stem cell fate, with matrix stiffness and viscoelasticity affecting differentiation and self-renewal. The ability of the ECM to flow and dissipate stress, or viscoelasticity, also influences stem cell behavior.Mechanical forces significantly influence stem cell behavior during development and regeneration. Stem cells and their microenvironment communicate through mechanical cues to regulate cell fate, behavior, and developmental processes. During embryonic development, mechanical forces pattern tissues and organs, while in adult tissues, mechanical interactions with the extracellular matrix (ECM) maintain stem cell potency. In vitro, synthetic stem cell niches can precisely control biophysical and biochemical properties to study how mechanical cues, such as matrix stiffness or applied forces, direct stem cell differentiation and function. Understanding stem cell mechanobiology informs the design of artificial niches for regenerative therapies. Mechanical cues guide development by influencing cell-cell adhesion, tissue morphogenesis, and stem cell fate. Intrinsic and extrinsic forces drive early embryo development, with contractile mechanical cues enabling self-organization and germ layer specification. Intrinsic forces, such as those generated by actomyosin complexes, regulate embryonic morphogenesis, including axis elongation and gastrulation. Extrinsic forces, like fluid shear, also influence development by signaling through primary cilia and generating morphogen gradients. Cell-ECM interactions guide later development, with ECM stiffness and composition affecting stem cell behavior. Mechanical forces regulate organogenesis by directing progenitor cells to specialized functions. For example, mechanical forces in the developing lung support smooth muscle development, while shear forces in the heart promote hematopoiesis and cardiac morphogenesis. Mechanical cues also influence multi-scale developmental processes by connecting macro-scale physical inputs with nano-scale molecular signals. Complex patterning depends on cell-ECM interactions, with physical traction forces on the ECM promoting the formation of organized structures. The mechanical properties of the ECM regulate mammary gland morphogenesis and angiogenesis, with matrix stiffness affecting biochemical signals and cell fate. The study of mechanobiology is complex due to the influence of mechanical stimuli on multiple aspects of cell behavior, including matrix traction forces, membrane curvature, and cell fate. Synthetic niches with tunable mechanics are used to study how mechanical cues regulate stem cell behavior. These systems allow independent control of mechanical, matrix, and soluble cues, enabling the investigation of how mechanical properties influence stem cell mechanobiology. 3D systems provide more accurate mimicry of in vivo environments, with mechanical properties and diffusion affecting stem cell behavior. Alginate systems are suitable for studying how physical parameters influence stem cell mechanobiology, as they allow independent regulation of crosslink density, stiffness, and viscoelasticity. Extrinsic forces can be applied to stem cells in bulk or microscale systems to directly probe mechanoresponses. These forces, such as cyclic strain or hydrostatic pressure, influence stem cell behavior and can be combined with micro-scale measurement techniques to study mechanotransduction. Mechanical cues regulate stem cell fate, with matrix stiffness and viscoelasticity affecting differentiation and self-renewal. The ability of the ECM to flow and dissipate stress, or viscoelasticity, also influences stem cell behavior.