Grassmannian cluster algebras recently are found to be important in scattering amplitudes in physics. In this talk, I will explain how to obtain explicit formulas of the dual canonical bases of Grassmannian cluster algebras C[Gr(k,n)] by using representations of quantum affine algebras and representations of p-adic groups. In particular, I will show that the dual canonical basis elements of C[Gr(k,n)] are in one to one correspondence with semistandard Young tableaux. A part of the semistandard Young tableaux correspond to cluster variables in C[Gr(k,n)]. We apply machine learning method to classify cluster variables. This is joint work with Wen Chang, Bing Duan, Chris Fraser, and with Man-Wai Cheung, Pierre-Philippe Dechant, Yang-Hui He, Elli Heyes, Edward Hirst.