Neuron Fly

Neuron flies look like two thin tails connected to a spherical floating body with a white eye (or face) and come in the colors red, white, blue or purple. They are prevalent in Five Pebbles​ and a small number can be found in Looks to the Moon. Consuming a neuron fly provides one food, and doing it for the first time in a save file will allow the slugcat to generate its own light for the rest of the game.

After eating a Neuron fly, aside from providing light, ghosts of the yellow overseer will appear randomly, either as a small ball wich dissipates on contact or flying trough the screen

Looks To The Moon
When Big Sister Moon is found, five neurons are flying above her. Catching these neurons causes Moon to shake her head frantically. Eating it makes her throw herself to the ground and jerk around. Eating all of them will kill Moon and earn the "Stolen Enlightenment"  achievement. If you don't eat them and hibernate, you earn "A New Friend" achievement.

From then on the Overseers will point to where to get more neuron flies for Moon. Following the Overseers will take the player to Five Pebbles, and require them to carry the neuron flies by hand back to Big Sister Moon. Upon delivering more flies to Moon, she will gain the ability to read pearls found in the world.

Tips and Trivia

 * Neuron flies lose the ability to fly or move outside of the two regions in which they are found. This makes carrying neurons between the two iterators possible but still challenging.