A scheme for programmable nanoscale self-assembly that allows the precise arrangement of components in 2D or 3D geometries would have a wide range of applications. The ultrasmall size and programmability of the nucleotide subunits in DNA offer a versatile basis for such a scheme. In this paper, I discuss recent steps toward nanocomponent assembly by 2D DNA scaffolding, including 1) incorporation of 1.6-nm Au nanoparticles in a 2D DNA scaffolding, 2) in situ assembly of 5-nm metallic nanoparticle arrays with precisely controlled dimensions and 3) sequence-encoded assembly of different sized nanocomponents in a common scaffolding. In the near term, this ability to precisely assemble nanocomponent arrays could enable the study of electronic, magnetic and plasmonic interactions among particles in a regime where quantum confinement, Coulomb blockade, and magnetic effects play important roles. Eventually, such self-assembly techniques could lead to a manufacturing technology for nanoelectronics, nanophotonics, and nanosensing.