Glass

"Glass, you see, can't be broken with regular tools in Minecraft. Well, not without it shattering into a million tiny, invisible shards. Any experienced builder will always cook up more glass than they need for this exact reason - the tiniest slip and you'll have to make a lengthy trip back to the desert for more sand."

- Duncan Geere

Glass is a decorative, fully transparent solid block that can be dyed into stained glass.

Natural generation
Magenta stained glass naturally generates as windows in end cities.

A secret room containing glass can be found inside woodland mansions.

Obtaining
Glass drops itself only if it is broken with a tool enchanted with Silk Touch; otherwise, it drops nothing.

Trading
Journeyman-level librarian villagers have a 50% chance to sell 3 glass for 1 emerald.

Journeyman-level librarian villagers have a $2/3$ chance to sell 4 glass for 1 emerald.

Usage
Glass blocks adjacent to other glass blocks are invisible when viewed through glass.

As a solid block, zombie reinforcements can spawn on top of glass, resulting in unexpected zombies "sneaking into" an otherwise secure area of a structure.

Redstone dust and components can be placed on glass but cannot power glass. Glass can't cut vertical redstone. Vertical redstone can be placed on glass. $$ it will only transmit redstone signal up, not down. Otherwise, glass in redstone circuits is functionally the same as an upside down slab.

ID
Java Edition:

Bedrock Edition:

Block data
In Bedrock Edition, stained glass uses the following data values:

Trivia

 * Before stained glass was added, there was a similar block named tinted glass in the April Fools version 2.0, which had the same use. The texture for the April Fools block was used before it was replaced.