I have come across it in Crash Course Anatomy & Phisiology. It is at around the 2th minute. Here it goes:
Although physicions 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.
Best Answer
To "get all up in something" is relatively recent slang (no more than 15 years old), and should probably not be used in any formal context. Roughly translated it means "to get extremely (possibly uncomfortably) close to something or someone".
Without additional distinction (i.e. "get all up in that") you can probably assume some kind of crude sexual connotation.
In the source you mention the author uses it ironically, possibly in order to make the text feel more accessible to young people. In my opinion it's awkward, like someone who has never been cool who uses a certain slang (incorrectly) to try to sound more cool ... but other people might like it.