Catalytic gas-phase synthesis of carbon nanotubes is gaining importance on industrial as well as lab-scale level. The method benefits from being selective toward single, double or multiwalled nanotubes as well as continuous, which makes it suitable for large-scale nanotube production. The nanotube synthesis research has been mainly directed to selectively grow the desired product. However, the fundamental understanding of the growth mechanism of the various nanotube structures has been mostly neglected. This presentation shows detailed experimental data on nucleation and growth of individual nanotubes from iron catalysed CO and ethanol decomposition. Coupling the knowledge of the growth mechanisms of the individual nanotubes with large-scale synthesis is of outmost importance. This presentation also covers the development of a pilot-scale nanotube production unit and describes the high degree of product control achieved in the process.