First off, you don’t have to worry about this whole universe-obliterating Big Rip thing for quite some time — the cosmos will not be big-ripped apart sometime next Tuesday, or even the Tuesday after that. So take a deep breath, keep your appointments, and exit your apocalypse bunker. As Wired says, if the Big Rip does happen, it’ll happen in about 22 billion years. Long before that far-flung 22 billion years in the future, however, the sun will expand into a red giant and consume Earth (per Astronomy), our Milky Way Galaxy will fuse with the Andromeda Galaxy (per EarthSky), and humanity will likely be long-dead — just to keep things in perspective. But for those readers banking on an immortal soul, or who are looking forward to the old consciousness-in-a-box mind upload, well … sorry.
As the esteemed Neil deGrasse Tyson explains in his interview with Stephen Colbert (watchable on YouTube), space itself is expanding. Galaxies themselves are stuck together, so they stay whole even as the space around them expands. In the same way, individual objects — stars, planets, you, your latte — remain stuck together as well. But eventually, the forces fueling the expansion of the universe may overcome the molecular, even atomic, and then sub-atomic forces binding the very fabric of spacetime together. If that happens then space itself, down to every single errant quantum particle, will separate into an infinitesimal nothing.