Discerning what the largest “thing” in the universe is much more difficult than it sounds. First, you must define what constitutes a “thing” since celestial objects could contain more than a single object that composes its whole.
Quantum physics is mind-bending, counterintuitive, and close to impossible to understand. It’s so complicated that a theory saying our reality is just one of an infinite web of infinite timelines is one that’s actually simpler than what most quantum physicists believe.
This interactive Flash animation titled “The Scale of the Universe 2”, covering everything in the universe from the fabric of space-time to the estimated size of the universe, was posted earlier in 2012, and it is awesome.