Stem cells can be guided to grow into bone or cartilage through the use of molecular cues provided in a 3D environment. Researchers developed a hydrogel nanocomposite containing halloysite nanotubes doped with growth factors that provides structural support within the gel. When mesenchymal stem cells and pre-osteoblasts were cultured in the nanocomposite, they differentiated into osteoblasts, proliferated, synthesized type I collagen matrix that mineralized, and increased protein synthesis including bone-specific proteins. This approach allows control over cell behavior and differentiation in 3D to engineer complex tissues for regenerative medicine.