The scale of the learning is interesting in itself. From a few months, to years old, to all the way to preteens, emotions are constantly being reevaluated and developing new ones as well.
Along with having a suite of emotions and recognizing cues in others, it's pretty obviously a required piece of learning to read emotion for humans. Below a certain age, it's literally impossible to generate ideas like "the cat doesn't like that", since there's no space between "I like that" and "that is likable". But I don't think I've ever seen somebody describe what kind of structural or chemical changes are correlated with e.g. passing the mirror test.
The self conscious emotions, pride, shame, guilt, envy, remorse, embarrassment, hubris, and many more come from the prefrontal cortex. As it develops over a very long period of time, so do the emotions. I remember that embarrassment doesn't typically develop until you're approximately 7-years-old.