The word you're looking for is "grok". The word was coined by Robert A Heinlein in his science-fiction classic "Stranger in a Strange Land". It implies an understanding of, and identification with something that is so deep and complete that it happens almost on a molecular (or soul-deep , if you prefer) level.

The term was fairly well-known to those of us who were about in the big bad 60's. I even remember Star Trek fans with buttons that said, "I Grok Spock"!