Controllable synthesis of horizontally aligned single walled carbon nanotubes (SWNTs) with specific chirality and high areal density remains a challenge.A recent breakthrough was achieved by the Jin Zhang's group from Peking University.They proposed a feasible route towards tuning the chirality of epitaxially-grown aligned SWNTs according to the designed catalyst lattice symmetry.With different uniform metal carbide catalysts,two different types of aligned SWNTs with specific structures, the metallic (12,6) and semiconducting (8,4) ones,can be synthesized separately with their chiral selectivity both over 80%,tandem with a high density of more than 10 tubes/μm.These exciting results clearly demonstrate that it is possible to control SWNTs'structures based on the symmetry matching in structures between SWNTs and crystal surface of catalyst particles.