It was IIJIMA's observation of multi-wall CNTs (MW-CNTs) (see Fig. 2.1) in 1991  that heralded the entry of many scientists into the field of CNTs, stimulated at first by the remarkable one-dimensional quantum effects predicted for their electronic properties, and subsequently by the promise that the remarkable structure and properties of CNTs might give rise to some unique applications. Although the initial experimental observations were for MW-CNTs, SW-CNTs had been the basis for a large body of theoretical studies and predictions that preceded their experimental observation. The most striking of these theoretical developments was the prediction that CNTs could be either semiconductors or metals depending on their characteristics, namely their diameters and the orientation of their hexagons with respect to the CNT axis (chiral angle) [16,17,18]. Though predicted in 1992, it was not until 1998 that these predicted remarkable electronic properties were corroborated experimentally [19,20].