Diamondoids are cage-like hydrocarbon molecules where the arrangement of carbon atoms resembles the lattice of diamond. Their sizes lie in the transitional regime between organic molecules and nanocrystalline diamond, which offers exciting opportunities to study the physical and chemical properties of diamonds at sub-nanometer scale. Here in the Melosh group, we have the unique capability to separate a wide variety of diamondoids with different sizes and conformations. Working in close collaboration with Z.-X. Shen group at Stanford and Peter Schreiner group at University of Giessen, we focus on creating novel self-assembled structures with chemically functionalized diamondoids, understanding their electronic, thermal and mechanical properties, as well as exploring their technical applications. Our ongoing research includes new chemistry for stable surface bonding of diamondoids, diamondoid-enabled advanced electron sources, diamodoid-directed assembly of low-dimensional materials, and utilizing diamondoids to seed the growth of diamond nanostructures.