Dictionaries state that "at the beginning" is often used with of. For example, at the beginning of the month/book/movie and so on. But I assume of isn't obligatory, right?
Cambridge Dictionary gives such an example:
I enjoyed my job at/in the beginning (= when I started it), but I'm bored with it now.
Well, is it ok to say something like this?
This really is a very large field and we are just at the beginning.