expression or idiom for a person who knows every detail about something


I was wondering if there's an idiom or expression for a person who knows everything there is to know about his field of interest or expertise, practically no detail is unknown to them.


I thought of the expression: knowing like the back of hand, but I guess that has a geographical sense to it and is used for cities, streets and neighbourhoods. (Please correct me if I'm mistaken.)


I hope I was clear. Thanks in advance.




Comments

Popular posts from this blog

etymology - Origin of "s--t eating grin"

First floor vs ground floor, usage origin

usage - "there doesn't seem" vs. "there don't seem"

pronunciation - Where does the intrusive R come from in “warsh”?

Abbreviation of "Street"

etymology - Since when has "a hot minute" meant a long time?

meaning - What is synonyme of "scale"?