Nature is inherently playful; think of a squirrel falling off a branch into a stream (I'll never forget seeing that as a kid), birds soaring on thermals for no "reason," or dolphins cresting waves. But once we become adults, most humans find there is little room for play, and urban environments are especially regulated and organized so that usually they don't feel very fun or festive. And often, they don't even feel particularly human, even though we design and live in them.

Enter guerilla knitting, the practice of taking boring public surfaces — lamp posts, poles and bike rack — and making them colorful and patterned by covering them in hand-knitted fabric. First attributed to the Knitta Please group out of Houston, Texas, in 2005, the practice quickly spread throughout the world, and is especially popular in Europe and Australia.

Also called yarn bombing, graffiti knit and knit tagging, it is considered street art and textile art at the same time. Check out some of the fun videos of this public art below.

Knitting in action! A pole in Marianblad.

A tree in Mainz.

Yarn bombing in Madison, Wisc., as part of a public art project.

Interested in learning more? Check out the teaser for the Yarn Graffiti doc that is currently in production.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.