Time for a different type of article.

Last of Us (Game) players know about this as this is the reason of the game. This fungus controls the mind of the host it infects.

Ophiocordyceps unilateralis is fungus, currently found in tropical forest ecosystems (Eg:Brazil). It infects ants. When the fungus infects a  ant, it grows through the insect's body, draining it of nutrients and hijacking its mind. Over the course of a week, it makes the ant to leave the safety of its nest and move to the nearby plant stem.

Then the fungus(along with it's host) looks for  an area with a temperature and humidity suitable for fungal growth (mostly 25 cm from the ground on a nearby plant stem). Then it stays there eventually the host dies . Few days pass and the fungus reaches reproductive stage where it sends a long stalk through the ant’s head, growing into a bulbous capsule full of spores. The spores rain down onto its colony, zombifying them in turn.

Another species similar to that: Ophiocordyceps sinensis

Unlike Ophiocordyceps unilateralis, This one affects caterpillars.

For more info visit wikipedia: https://en.wikipedia.org/wiki/Ophiocordyceps_sinensis

Why does it do that?

The answer is simple. For self-propagation.

That's it for now. I know this article is going to give chills to many.