FlowScopes are devices which allow people to see and influence the fascinating behavior of turbulent fluids.
These turbulence patterns are all around us - for example when we move through air or pour a glass of water - but are normally invisible due to the uniformity of the fluids involved.
The key elements of a FlowScope are a transparent container of rheoscopic fluid, a stirring method, and effective lighting.
Such fluid visualization devices can take many forms, I've built flat panel, cylinder and spherical versions.