We introduce rhombic tableaux to give new combinatorial formulae for Schubert polynomials in a partial flag variety G/P. In the case of Grassmanian, our rhombic tableaux are exactly (reverse) semistandard Young tableaux. We discuss extensions to Stanley symmetric functions and K-theory, as well as a generalization of Bender-Knuth involution. Joint work with Ilani Axelrod-Freed and Jiyang Gao.