Do you know what movies introduce the concept of microexpressions?

No I don’t. I’m not even sure if I want to learn what the concept of microexpressions supposedly is.

Micro expressions are not a concept that was introduced, they are a categorization of facial expressions that have always been present.

The earliest silent films had the actors display exaggerated forms of micro expressions so that the emotional undercurrent could be communicated. All Ekman did was catalog and enumerate them.