S. Iijima was first to recognize that nanotubes were made up of concentric rolled graphene sheets with a large number of potential helicities and chiralities, rather than a graphene sheet rolled up like a scroll, as originally proposed by Roger Bacon. Since their discovery, carbon nanotubes have been of great interest, both for the elucidation of fundamental one-dimensional science and for a wide variety of potential applications. Chemical vapor deposition allows the production of nanotubes to occur at predetermined locations via patterning, and well-oriented arrays are possible through gas flow or electric field alignment. The nanotubes and by-products are collected via condensation on a cold finger downstream from the target. In gas phase growth, the catalyst formation and nanotube growth occur literally in mid-air. In substrate growth, once the nanotube begins to grow by either surface or bulk carbon diffusion, the carbon nanotubes will undergo either base growth or tip growth.