Hover over the image to show the baseline grid:

This page from the latest issue of 8 Faces shows how important the baseline is: the body type (at 7.5pt / 11pt) dictates the baseline grid and then everything else aligns to it. The small red text uses incremental leading to match every fifth line of its own type with every fourth line of the body type. The pullquote’s type is sized so that the x-height of each character takes up one baseline increment, as does the height of the borders above and below the quote. The images, too, follow the same baseline grid.

Related blog post: The relevance of the baseline grid