Abstract: Have you seen the movie "Ant-Man"? The world seems very different, depending on your size (scale). People have developed the "physics" of different scales, for example, fluid dynamics for everyday scales, kinetic theory for smaller ones, and molecular dynamics for even smaller ones. One natural question would be: is the world fundamentally, not only apparently, different, depending on your scale? One way of approaching this question is to figure out if we can derive physics (equation) of larger scales as a reasonable limit of that of smaller scales. In this talk, we will briefly take a look at such scaling limits.