IRG3 exploits unique synthetic capabilities in high-pressure infiltration of semiconductors into diverse 3D nanotemplates to create new materials in which electronic, magnetic, and vibrational degrees of freedom interact with well-ordered nanometer-scale 3D structural modulations. Rigid nanotemplates will induce multi-GPA stresses onto semiconductors such as silicon that contract via crystallization within them, thereby tuning band gaps by nearly 2× while also varying other properties such as mobility and dopant solubility. Ordered, electrically continuous 3D structural modulations of extreme strain, quantum confinement, and interfacial physics will define a new physical regime for electronic, optical, magnetic, and thermal response, one that exploits diffraction effects to control thermal and electrical transport. The greatly altered palette of physical properties thereby made available in well-developed semiconductor platforms such as Si could enable practical application in diverse areas such as solar cells, near-IR photonics, light emitting devices, and improved thermoelectrics.