In West Philadelphia, a group of teenagers have been working with artists, counselors and teachers exploring what "home" means. It's organized by the Mural Arts project. The young people's photos and stories inspired public health researchers to look closely at an aspect of urban teenage life that is dangerous and under-reported. 

Just mention the word homeless and images of men sleeping on the sidewalks or under bridges may come to mind. They are the most visible homeless people, but there's an entire population of teens who don't have a stable place to spend the night or get a meal. They're called "home insecure" youth and they are mostly invisible.

"I think because you don't see homeless kids, young adults is because they're moving house to house or because they don't like it or their parents kick them out," said a young homeless person who did not want to be identified.

He's one of the 35 young people who shared their stories. The Mural Arts project "A Place to Call Home" documented their precarious living situations. University of Pennsylvania public health professor Carolyn Cannuscio says poverty is the common denominator in their lives.

"In Philadelphia if you want to look at the extremes, in 2009, 3500 children 17 year old and younger did not have a home at some point during the year," said Cannuscio. "But when we want to look at poverty more broadly 40 percent or families in north central Philadelphia are living at or near the poverty line, that a high degree of poverty."

Zachary Wood agrees. He's the development director of Philadelphia's Covenant House, a chapter of the one of the largest national organizations helping homeless youth. Every night, he says, Covenant house shelters 50 or so Philadelphia teens, but reaching "home insecure" youth has proven elusive.

"What we've seen is a lot of young people even inside the school system who are bouncing from house to house--staying with friends, relatives, Granma--bouncing around that technically would under the homeless definition," said Wood. "They don't see themselves that way and even if they did they don't want anyone to know that."

"I've been homeless before until my dad kicked me out, after I dropped out of school to help pay the bills," said another teen.  "After he got better and start doing what he does, he kicked me out. I was home and I ended up sleeping under the boardwalk and ended up at Covenant house."

This 21 year-old, who lived for a while in Atlantic City, is now the doting father of a two year old boy. By participating in "A Place to Call Home" he connected with services and is earning his GED. In telling their stories, the students invariably defined home this way.

"Home for me is a safe place --- a quiet place. When I'm my home I feel safe, relaxed I feel like myself when I'm in my home, when I'm outside my house I don't feel as safe as I want to be."

"Honestly these kids have to be so vigilant all the time and they know it," said Carolyn Cannuscio.  "They live their lives under the threat of gun violence in the city. They all talk to us about the gun shots they hear. boom boom boom, in their neighborhoods. They dream of a place with no gun shots. They're not sure if such a place exists."

Cannuscio has just released a study on housing and young people's health, based on the teen's interviews.

"In the long term they're experiencing more chronic illness," she said. "They're more likely to die young from chronic diseases , even if they survive the gun violence in their neighborhood."

"My house is not a good place to be, there's a lot of stuff going on," said one young woman.  "It's cold, there's people in the house that do nothing and just sit around. Sometimes they'd be fooling, like my mom when she goes shopping, they try to fight on me or have an attitude. There's too many drugs."

Right now, there aren't too many places for teens to get help finding housing, a job or health care. Many service organization are better set for an older homeless population or for temporary shelter. Reverend Charles Howard, chaplain at the University of Pennsylvania, says their stories speak of resilience and a reluctant measure of hope.

"They ran away so they could thrive as a survival tactic," said Howard. "That's really sad. Yet it also speaks of the courage of a lot of folks in the streets. It takes a great a great heart to navigate life on your own at 13, 14, 15, That's a tough kid and a kid that can do something special in this world if given the opportunity."

But before these young people can get that opportunity, they have to come out of the shadows. This project proves how much work it takes to build enough trust for them to risk asking for help. The next step is for society to deliver on the promises.