Considering the structural parameters, the diameter of the nanofibers has been determined to have the major impact on the properties of the resultant CNFs. During the electrospinning process, the fiber diameters obtained are dependent on the jet size, and the polymer contents in the jet. As the polymer solution jet travel from the tip to the metal collector, the main jet gets split into multiple jets, giving rise to various diameters. The diameter of the electrospun nanofibers can be attributed to four factors: (i) faster conversion of electrospun precursor fibers into CNFs are achieved for the smaller fiber diameter, which can significantly decrease the time, and energy consumption during air stabilization, and carbonization, (ii) the smaller the fiber diameter, the larger the number of cross junctions between nanofibers, which may eventually lead to better mechanical properties, and higher electrical conductivity of the resultant CNF web. (iii) higher flexibility of the CNT mat could be obtained for a smaller fiber diameter due to a significant decrease of bending stiffness; and (iv) the core-shell structure of the CNFs could be greatly lowered, if the precursor fiber diameter is reduced to the nanoscale, due to the improvement of thermal conductivity accompanying the thermal uniformity across