The yellow region is true vacuum, and the red region is false vacuum. The teardrop-shaped region at the bottom represents the child universe, which has recently detached from the parent universe. The false vacuum region will continue to expand, producing an inflationary universe that is completely disconnected from its parent universe.
For more information see S.K. Blau, E.I. Guendelman, and A.H. Guth, Phys. Rev. D35, 1747 (1987), and also E. Farhi, A.H. Guth, and J. Guven, Nucl. Phys. B339, 417-490 (1990); or click here for a list of relevant papers.