A self-assembled hybrid of ultranano-crystalline diamond (UNCD) and carbon nanotubes (CNTs) is successfully prepared by their simultaneous growth in an argon-rich Ar/CH4 plasma (see Figure and cover). Control of the relative fractions and configurations of UNCD and CNTs in the hybrid material is demonstrated. This new synthesis pathway enables the development of new nanocarbons with unique mechanical, tribological, and electrochemical properties.