Why does frozen milk turn back into milk?
When you thaw milk again why does it completely reconstitute back into the milk?
Well, it's all about energetics. In other words, when you bring the temperature back up you've got molecules of water bumping into each other and the consequence of that is that the particles of milk reform into these little cells which then spread out evenly through the milk. That's the most energetically stable way for them to organise themselves.