What is an Emulsion and how to make a good one

What is an emulsion ✓ An emulsion is a dispersion of two immiscible fluids one into the other. ✓ To disperse one phase into another we reduce one phase (dispersed phase) into small droplets and we disperse them into the outer phase (continuous phase).
 To have a good emulsion we need to have an homogenous dispersion (similar size of droplet of dispersed phase) and it has to be stable too (no demixing or coalescence phenomena). 
Using a centrifugal pump to push liquid through a narrow slot improves velocity and then reduce particle size (typically to micron range). This is what a rotor-stator does.