Tian Lan is an assistant professor at Chinese University of Hong Kong. During his undergraduate years, he had the valuable opportunity to study both mathematics and physics at Tsinghua University. Guided by Liang Kong, he entered the realm of category theory and his fundamental philosophy has been converted ever since: it is all about morphisms. His PhD research later at Perimeter Institute, under the supervision of Xiaogang Wen, focused on the interplay between symmetry and topological order. He then moved to Institute for Quantum Computing as a postdoctoral researcher and completed work on the classification of 3+1D topological orders. Recently, he is pursing a comprehensive higher categorical formulation for generalised symmetry and topological defects.