In this talk, we discuss several mathematical problems related to the compressible fluid. In the first part of the talk, we mainly focus on the derivation of the compressible fluid equations from various physical models, such as particle, quantum and kinetic models. In particular, we discuss the rigorous derivation of the compressible fluid model, directly from the quantum mechanical models by using the method of modulated energy. In the second part of the talk, we turn our focus to the study of compressible fluid itself. Specifically, we present the stability of the shock wave of the one-dimensional barotropic compressible Navier-Stokes equations on the half-line. Our methodology of obtaining the stability is based on the method of a-contraction with shift.