What's the Fabric of space made out of?

Hi, I have only gotten to this post so far in the thread, but isn't this the book where Brian Greene talks about "space tearing flop transitions?" So maybe the poster that stated that space doesn't stretch or tear was wrong? We are told all the time that one of the ramifications if general relativity is that space bends in the presence of matter and that "straight" trajectories become "curved" trajectories. Space has to be "something" to me if it can react to the presence of matter (unless matter is a wrinkle in space itself) and also have energy (the vacuum energy).