A teenage girl's mind was completely blown when she learned a basic fact about our planet.

Twitter user @LoveMahalHappy posted a now-viral video that captured the very moment her sister learned that humans live on the surface of Earth and not inside it.

"I thought we were living inside!" she shouts, visibly shook. "Oh my gosh. I thought this whole time we were living inside the earth."

Her father then chimes in, suggesting she should've learned this information in science class.

"Dad, they never told me that we were living on top," she responds, before drawing a picture of how she previously believed the planet was structured. As you can see in the video below, the child assumed that the world was a dome and that all life was situated on the bottom.

"We're not [in] a snow globe!" her sister informs her. 

You can watch the girl's reaction below.