In this talk, I will talk about the categorification of quantum groups using quiver Hecke algebras. In the first half of the talk, I will explain definitions for quiver Hecke algebras and the idea for categorification using quiver Hecke algebras. In the second half, I will show applications of quiver Hecke algebras in viewpoint of representation theory including my recent result on tensor products [arXiv:1804.11056]. If time permits, then I will explain open problems in this area.