... Many problems concerning convergence of solutions of the Navier Stokes and Boltzmann equations to the Euler equation are wide open In this presentation I want to emphazise some similarity between the two problems with several examples: Eternal solutions of the Boltzmann equation, Boundary effect both for Boltzmann and Euler etc This will be a pot pourri, but as such it is based on several papers with several authors: Irene Gamba, Francois Golse, Dave Levermore, Lionel Paillard and Edriss Titi. ...