This lecture explores the relationship between electron energy and crystal structures in transition metals, focusing on BCC, FCC, and HCP structures. It discusses the empirical observations of crystal clustering in the periodic table, the evolution of crystal structures in Lanthanides, and the analysis of hexagonal close-packed structures. The lecture also covers the c/a ratios of hexagonal crystals, the anisotropy in properties of non-ideal hcp crystals, and the manifestation of anisotropy in physical properties like thermal expansion and electrical conductivity.