Interfaces: To be avoided or to be treasured? What do we think we know?

Whatever our specific field of expertise, we all have to deal with interfaces, whether we are involved in designing the large interfaces in high voltage cable accessories or whether we try to tailor the interface properties on a very small scale in nanocomposites. Whereas many of us study the properties of new insulating materials and their bulk properties, this paper focuses on what we think we know about interfaces and how to deal with them, and on where we definitely lack knowledge. The storyline will go from the scale of centimeters, to micrometers and it will end at nanometer scale. It will be shown that the way we need to look at interfaces changes drastically when we go down in size.