The book exposes the revelation of the existence of a NUCLEAR ZONE in clusters. This is the region in which clusters have nuclear centres comprising some of the skeletal elements of the clusters. The nuclear zone is a function of (n) the total number of skeletal elements. The limits of the nuclear zone are given by Ki=2n-1 and Kf=3n-1. The corresponding capping symbols are C0+Dn (C0Dn) to Cn+D0(CnD0). The nuclear zone limits Ki and Kf have provided another method for determining K_= Cy + Dz from which cluster valence electrons can be calculated. This method is faster, shorter and easier than the previous one.