Minecraft wiki entry for Glass_Pane, associated text: The screenshot that Jeb posted on his Twitter.
Glass panes in the 1.8 Pre-release.
Panes are thin, so it is possible for players or mobs to fit in a 1×2×1 space, which makes them useful for creating trophy displays, like this Creeper here.
Water does not flow through the holes in the panes, but the player can fit inside them.
The original look of stained glass panes.
Stained glass panes as of 1.7.2.