Tiny Bubbles...
In 1995, a physicist named Neil Turok worked with Martin Bucher and Alfred Goldhaber in creating an inflationary, open universe theory. Turok explains the theory in this manner:
The process is a bit like the formation of a bubble in a boiling pan of water...the interior of this tiny bubble manages to turn itself into an infinite open universe. Imagine a bubble forming and expanding at the speed of light, so that it becomes very big, very quickly. Now look inside the bubble.
The peculiar thing is that in such a bubble, space and time get tangled in such a way that what we would call today's universe would actually include the entire future of the bubble. But because the bubble gets infinitely large in the future, the size of 'today's universe' is actually infinite. So an infinite,open universe is formed inside a tiny, initially microscopic bubble.
Although Turok disliked the fact the theory could not explain what came before inflation, he gave lectures on open inflationary universes in Cambridge and caught the attention of Stephen Hawking. Hawking suggested that Turok cast his ideas in the frame of the Hartle and Hawking No-Boundary theory. After doing so, they realized that all inflationary theories produced open universes in the manner Turok described above. In the end, they created the Hawking-Turok Instanton theory.