In this talk, I will present our latest result on atomic-structure-based separation of single-wall carbon nanotubes (SWCNTs) by DNA, as well as the controlled assembly of SWCNTs via DNA hybridization. In particular, I will describe a quick and easy precipitation based sorting method, a simple pattern underlying many DNA sequences that recognize specific SWCNT structures, and a robust process to wrap SWCNTs by DNA sequences to enable many different applications, including controlled assembly of SWCNTs.