I can give you some examples of microaggression . When my youngest son was in university he befriend a young fellow from Nigeria . He brought him home and soon the boy was at my house all the time. One summer he pretty well slept on my couch all summer. On one occasion we went out to a restaurant and after ordering our meals from the waitress he said " Did you see the way she looked at me ?" . " Yeah I did" said my son " She smiled at you and asked you want you wanted ".  " No , there was more " his friend replied. My son said " Dude , we were watching her while she spoke to you ". 
This type of incident happened more than once.
My daughter is a cop and when she pulls over a car for speeding , if it's a nonwhite  driver and they see she's a blond woman , she will often be called a racist for pulling them over.
There's another microaggression.