SPH is a particle method for fluid dynamics. I will discuss how the Lagrangian basis for SPH leads to the conservation laws. The most remarkable of which is circulation which can be conserved accurately by SPH. The SPH integration without dissipation cries out to be implemented using a symplectic integrator. The application of the Verlet integrator to self gravitating gaseous disks will be presented and the easy generalization of SPH to relativistic fluid dynamics, and thus to a relativistic particle system, will be discussed.