Here are some examples:
* ¿En qué ciudad vives? (In what city do you live?)
* En qué momento ocurrió el accidente? (At what moment did the accident occur?)
* En qué se diferencia tu trabajo del mío? (In what way does your work differ from mine?)
It's important to note that "en qué" can also be used as a preposition meaning "in which" or "in what."
* La casa en qué vivimos es muy grande. (The house in which we live is very big.)
* No entiendo en qué consiste el proyecto. (I don't understand in what the project consists.)