Glass Pane

Glass Panes are transparent blocks which can be used as an alternative to Glass. They are also similar to iron bars and fences. Glass panes were released in 1.8. Unlike glass, when destroyed you can pick it up again. Their placement behavior is similar to Redstone, Iron Bars, and Fences. They have the same texture as Glass. They cannot currently be placed horizontally. Glass Panes can be mined and picked up without being broken. (about 1:45 min) Glass panes are present in buildings of villages. When placed without anything on the sides of it it will appear in the shape of an X but when something is placed on the sides of it it will become flat or into a ┌ shape or a T shape depending on the items surrounding it.

The amount of glass to panes is very efficient. Reasons list as:
 * 1) You get the item back when you destroy it.
 * 2) You get more for less.
 * 3) Might be a better use in the building of mob towers(Unconfirmed)
 * 4) House Traps

You can use glass panes under water to build a chamber where you can restore your breath (1 block at head level is enough).

Crafting
Glass Panes can be crafted by placing 6 Glass blocks in a 2x3 rectangle.

Trivia

 * a 2x2 area made of glass panes can make a hole big enough for the player to fit through in the middle, but not rain, water, etc. this can be used as an easy entrance for an underwater house, but not an exit. Iron Bars work similarly.