The conducting polymer polyaniline can be synthesized in high yields as nanofibers with diameters less than 100 nm and lengths of up to several micrometers. The chemical oxidative polymerization of aniline is accompanied by a characteristic color change from colorless to deep blue then finally green as the polymer progresses through several oxidation states. By removing aliquots of the solution and subsequently formed precipitate at timed intervals and then quenching the reaction with ammonium hydroxide, it is possible to obtain �snapshots� of the material throughout its synthesis. Scanning electron microscopy reveals a morphological evolution from irregularly shaped clusters to extensive networks of nanofibers. This transition can be roughly correlated to the color change, and UV-Vis and FTIR spectroscopy suggest that nanofibers are not formed until the emeraldine state of polyaniline is achieved. The relative amounts of non-fibrous and fibrous materials, as well as the rate at which nanofibers are formed, are dependent on the pH of the reaction medium.