Hi Jamie,
The small universe breathing or the microcosmic orbit is a breathing method that allows anyone to start deliberately circulating the build up qi in the body utilizing the governing and conception vessels. For more details on these, search google for (du and ren vessels governing conception).
The attached pic with thumbnail below shows the small universe pathway. The pic isn't much bigger than the thumbnail
Only simple pic I could find of it.
When tongue is at roof of mouth and there is the in breath brining qi go the lower abdomen, on the outbreath, drop tongue, slowly blow air out mouth and visualize the qi moving downwards toward the anus, straight up the spine, over the head and down to the roof of the mouth...all on one outbreath. That is all one in and out breath.
repeat.
That is the "small universe" breathing. It can get more complex with all the theoretical explanations of what is happening but cultivating the qi in the dan tien first for a while is crucial or the qi will just fizzle out and be very weak through the system.
An enhancement of this is on the outbreath when dropping the tongue, contract the anus and that connects strongly the point down there. On the in breath relax anus and reconnect tongue to the roof of the mouth. etc...
Both switches at the top and bottom are 180 degrees out of phase from each other. When one is on the other is off and visa versa.
This system is strangely similar to the Bedini "free energy' battery chargers with the same style switching mechanism. Our body and these energy systems are all open systems.
The large universe is just a more complex pathway for the energy to be directed. If I can find a good pic, I'll post it here if not, I'll explain it here.