This is a tutorial on the concept of scale in Realflow. According to feedback from many fellow Realflow users, scale is often misunderstood or not taken into account at all. Therefore I created this tutorial, showing people how I usually work and that scale or realistic scale in dynamcis is mostly a concept for forces reacting on particles. Part one of this tutorial deals with Realflow's standard particles (SPH), only. Part two is meant to be focused on Hybrido and will be published here when it's done.