Game Level Design: Unreal: Blueprints: Scripting Sublevel Loading (Unreal 4)

When one level is part of another, it becomes a sublevel of the other, persistent level. With streaming volumes, Unreal will handle the load and unloading of sublevels as long as the viewport is within the streaming volume space.

In this video, blueprints node are used to dynamically cause the loading and unloading of sublevels. By using the Load Stream Level (and Unload Stream Level) nodes, dynamical level loading can be scripted and respond to events other than the viewport being inside the streaming volume.