I have come across the phrase "get all up in something" in Crash Course Anatomy & Physiology. It is at around the 2nd minute. Here it goes:
Although physicians and artists have been exploring human anatomy for centuries, histology, the study of out tissues, is a much younger discipline. That is because, in order to get all up in a body's tissues, we need microscopes.
I have checked all the meanings of the phrasal verb get up has, but none fits.