In the beginning was Nothing. No space, no matter or energy. But according to the quantum principle, even Nothing was unstable. Each bubble became an expanding universe. I find that a very satisfying picture.
Universes can literally spring into existence as a quantum fluctuation of Nothing.
But the universe itself may be a free lunch. Although this picture is appealing, it also raises more questions. The probability of forming these other bubbles is vanishingly small. On the other hand, Weinberg believes most of these parallel universes are probably dead. To have stable DNA molecules, the proton must be stable for at least 3 billion years.