Abstract: It is well known that the Schur polynomials satisfy the Hirota bilinear equations of the KP hierarchy,
 and that each Schur polynomial can be parametrized by a unique Young diagram.
 We also know that the KP solitons (exponential solutions) can be parametrized by certain decomposition of the Grassmannians.
 In the talk, I will explain the connection between the rational solutions and the KP solitons in terms of the Young diagrams.
 More explicitly,  I will show how one gets a rational solution from a KP soliton.
 I will also discuss a connection between quasi-periodic solutions (theta or sigma functions) and the KP solitons.