Formal:
* Elaborate: To explain something in detail.
* Expound: To explain something in a detailed and comprehensive way.
* Discourse: To discuss something at length.
* Delve: To explore something deeply.
* Analyze: To examine something carefully and in detail.
* Discuss: To talk about something in detail, often with the aim of understanding different perspectives.
Informal:
* Dig deep: To explore a topic thoroughly.
* Go into detail: To provide specific information about something.
* Get to the bottom of it: To fully understand something.
* Break it down: To explain something in a simple and understandable way.
* Pick apart: To analyze something carefully and critically.
* Unpack: To explore the different aspects of something.
The best word to use will depend on the context and the specific aspect of in-depth discussion you want to emphasize.