Nanomaterials synthesis. In his early work Lieber articulated the motivation for pursuing designed growth of nanometer-diameter wires in which composition, size, structure and morphology could be controlled over a wide range, and outlined a general method for the first controlled synthesis of free-standing single-crystal semiconductor nanowires, providing the groundwork for predictable growth of nanowires of virtually any elements and compounds in the periodic table. He proposed and demonstrated a general concept for the growth of nanoscale axial heterostructures and the growth of nanowire superlattices with new photonic and electronic properties, the basis of intensive efforts today in nanowire photonics and electronics.