Glow Lichen

Glow lichens are non-solid blocks, $1/16$ of a block in thickness that can be placed on all the sides of a solid block.

Natural generation
Glow lichen is naturally generated on, , , , , , and s underground. It generates more frequently in ravines. It can be generated underwater as well in oceans.

Post-generation
bone meal causes glow lichen to spread to random adjacent block if possible, otherwise the bone meal is wasted. By fertilizing one lichen with bone meal, it is possible to cover the sides and the top of an adjacent block, but not the back. Otherwise, glow lichen does not spread naturally.

Breaking
Glow lichens can be destroyed with anything, but using shears is the only way to collect them. Efficiency on Shears has no effect when used with glow lichens. Breaking them with an axe is the fastest, but does not allow for collection in Java Edition, whereas it does in Bedrock Edition.

Light
Glow lichen emits a light level of 7.

Composting
Placing a glow lichen into a composter has a 50% chance of raising the compost level by 1.

Trivia

 * If the player removes all directional states using a debug stick, the block becomes invisible but the light emission remains, unless another block is placed there.
 * In real life, the lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.