Stem cell differentiation is the fundamental biological process by which a less specialized stem cell transforms into a more specialized cell type with distinct morphology and function. As a core concept in developmental biology and regenerative medicine, this field investigates the complex molecular mechanisms, signaling cascades, and environmental cues that regulate lineage commitment, cellular maturation, and the generation of diverse cell populations essential for tissue development, homeostasis, and repair. Its study is paramount for understanding developmental processes, disease modeling, and developing cell-based therapies.