Mushroom

Mushrooms are plants that can grow in dark caves and shady areas. They are more readily available in swamp and mushroom biomes and the Nether due to its low light conditions. Red mushrooms are generally rarer than their brown counterparts.

Mushrooms can be collected without any specialized tools (by hitting) and planted on the ground in light levels below 13 (except in the case of Mycelium blocks, where mushrooms will remain planted even under full sun). Planted mushrooms will grow into Huge Mushrooms when bone meal is used on them, and will pop out of the ground if the light level goes above 12, water flows over them, or when pushed by a piston.

The individual blocks of Huge Mushrooms will drop individual small mushrooms when broken by the player. Oddly enough, the blocks cannot be set on fire and are unaffected by lava.

Mooshrooms are a unique mob that serve as a source for red mushrooms (when shorn) and Mushroom Stew (when "milked" by the player while holding a bowl).

Pre-Beta
In Creative Mode, mushrooms were a decorative item, having no crafting use and remaining in the ground when planted. In Classic, mushrooms could be placed on any block except another mushroom, and would remain planted when the block below them was removed. During Indev, mushrooms were generated in rare instances under trees or in the shadows of other floating continents in the "Floating" map type. In Survival Test, Pigs were able to eat mushrooms. Brown mushrooms healed and the consumption of red mushrooms caused  damage to the player's health. From Indev onwards, red and brown mushrooms could not be eaten on their own, but could be crafted together with a bowl to yield Mushroom Stew.

With the addition of biomes and the dimly-lit Nether in Alpha 1.2.0, mushrooms became a more common sight.

Beta
The first 1.9 pre-release revealed the addition of the mushroom biome, an island composed of Mycelium blocks and populated by Huge Mushrooms and Mooshrooms, strange red cows with red mushrooms growing on their backs. The second 1.9 pre-release added a new crafting recipe involving brown mushrooms. Each one could be crafted with a unit of Sugar and a Spider Eye to produce a Fermented Spider Eye.

Trivia

 * Red mushrooms bear a strong resemblance to Amanita muscaria (Fly Agaric) mushrooms. In the real world, consuming these red mushrooms will cause delirium and hallucinogenic effects and death if their toxicity has not been reduced by parboiling. This is supported by the fact that eating the Red Mushroom caused damage to the player in the Survival Test.

Bugs

 * Rarely, A Mushroom maybe spawned above a Lake(See above)
 * Looks like mushrooms dont spread in pre-release 6.

Anomalies

 * Mushrooms can grow on trees.
 * Brown Mushrooms produce light (level 1), while red ones don't.

Pilze Mushrooms/es Champignons Gombák Paddenstoelen Grzyby Грибы Mushrooms/ch