Space seems fundamental. To build a universe, surely you need something to build it on or in. Many, maybe most physicists now think that the fabric of space emerges from something deeper. And perhaps the most existentially disturbing such proposal is that our 3-D universe is just the inward projection of an infinitely distant boundary. A hologram, or sorts. Let’s see how that can actually work, and what the holographic principle really says about the “realness” of this universe.