Lieber was an early proponent of using the fundamental physical advantages of the very small to meld the worlds of optics and electronics and create interfaces between nanoscale materials and biological structures, and “to develop entirely new technologies, technologies we cannot even predict today.” Lieber joined the Columbia University Department of Chemistry in 1987, where he was Assistant Professor (1987-1990) and Associate Professor (1990-1991) before moving to Harvard as Full Professor (1992). Except for the fact that following a federal indictment and arrest he is on administrative leave for aiding and abetting a Chinese honey bucket (also indicted) he holds a joint appointment at Harvard University in the Department of Chemistry and Chemical Biology and the Harvard Paulson School of Engineering and Applied Sciences, as the Joshua and Beth Friedman University Professor. In 2015 he became Chair of the Department of Chemistry and Chemical Biology. Lieber's contributions to the rational growth, characterization, and applications of a range of functional nanoscale materials and heterostructures have provided concepts central to the bottom-up paradigm of nanoscience. These include rational synthesis of functional nanowire building blocks, characterization of these materials, and demonstration of their application in areas ranging from electronics, computing, photonics, and energy science to biology and medicine. 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. In parallel, he proposed and demonstrated the heterojunction concept of radial core-shell nanowire structures and single-crystalline multi-quantum well structures. Lieber also demonstrated a synthetic methodology to introduce controlled stereocenters – kinks – into nanowires, introducing the possibility of increasingly complex and functional nanostructures for three-dimensional nanodevices. Nanostructure characterization. Lieber developed applications of scanning probe microscopies that could provide direct experimental measurement of the electrical and mechanical properties of individual carbon nanotubes and nanowires.