We have observed the extension process of individual single-walled carbon nanotubes (SWCNTs) on SiO2 substrate during chemical vapor deposition using in situ scanning electron microscopy. Cobalt-filled apo-ferritin was used for dispersion of Co catalysts on the substrate, minimizing overlapping of SWCNTs grown. The growth of a SWCNT exhibited an incubation stage before nucleation, a growth stage with an average growth rate of 3-5 nm/s, and termination of extension after the growth stage. It is likely that catalyst migration at the SWCNT tip occurred for continued extension of SWCNTs on the substrate. (C) 2007 Elsevier B.V. All rights reserved.