It happens all the time. People walking into glass doors that appear so clear, they don't realize anything is there. Videos of these collisions are all over the internet.
It even happened to Justin Bieber as he was going through a revolving door.
The videos may seem funny, but it's not always a laughing matter. Some people hit with such force, the glass breaks. And just this week at a student protest at Cal State University, a large glass window shattered in the lobby as students scuffled with the police.
The injuries from incidents like these can be devastating—severe lacerations causing scars that can last forever.
But as INSIDE EDITION's Lisa Guerrero demonstrated, it all depends on what type of glass you walk into.
If the glass you collide with is made of safety glass it will break into small pieces and you'll probably escape with just minor scrapes and bruises.
But if it's regular window glass you can get seriously injured by large shards with razor sharp edges.
That's what happened to 8-year-old Madeline Forman. Her forehead was sliced open when she accidently walked into a sliding glass door on a hotel balcony.
Her mother Kate found Madeline severely bleeding in a pile of glass shards.
"It was the most horrifying scene I had ever witnessed in my entire life. I can't describe what it's like to look at your child to see that their face is bleeding and know part of their face is now coming off," said her mother Kate Forman.
A hotel clerk immediately called 911: "We need an ambulance here. Someone walked through a glass window. They're cut bad."
Madeline was rushed to a the emergency room, where she received almost 70 stitches to close her deep cuts.
We had safety expert Don Mays at Consumer Reports along with a team of technicians assist us in demonstrating the difference between safety glass and regular window glass.
When we tried to break a pane of regular window glass, it broke into large shards of sharp pieces that can slice through skin like a razor.
When we tried to break the safety glass, at first, it didn't even break. But when it did, there were no large shards, just tiny pieces that are much less dangerous than the regular glass.
Madeline's parents want everyone to know about the hidden dangers you may not be aware of until it's too late.
Older buildings like the hotel where that little girl was hurt, are not required to have safety glass, which is mandatory in buildings built since the late 1970's.