I will discuss the characteristic initial value problem for the multi-dimensional compressible Euler equations. This is the initial value problem with data given on a pair of transversally intersecting hypersurfaces that are null with respect to the acoustical metric. The analysis relies on special structures in the PDEs that arise from restricting the fluid equations to null hypersurfaces. Another interesting feature of the problem is that even if the given “tangential data” are smooth, the transversal derivatives along the data hypersurfaces can develop singularities. The main result is local well-posedness in a future-neighborhood of the portion of the null hypersurfaces where the entire solution gradient is finite.