Approximately 2.2 million Americans are behind bars, according to the U.S. Department of Justice, more than in any other country in the world. My assignment from CNN was to put a human face on this number so we can better understand the implications of putting so many people in prison. The result is a three-part series that aired on "360" this week:

* Youth behind bars
* Stopping the revolving door
* Women in prison

As I dug into these stories, I came across some shocking numbers: Half of inner-city boys drop out of high school and 6 in 10 will spend some time in prison during their lives, according to the New York Times; also, of the hundreds of thousands of prisoners released every year roughly 50 percent can be expected to return within three years, according to a Department of Justice study. But perhaps most shocking are the numbers concerning women and prison:

* The women's prison population has grown 757 percent from 1977 through 2005, according to the Institute on Women and Criminal Justice
* 70 percent the women in prison or under correctional supervision are mothers, according to the Department of Justice
* 1.3 million children are affected, according to the Department of Justice

I'm not sure what I expected for a story about women in prison, but I have to say right off the bat that I had no idea it would be about mothers and their children. I was surprised to find that the majority of women behind bars are mothers who are very often the primary caretaker for their children. I hadn't thought so many children would be affected. I also had no idea that, according to the Women's Prison Association, 5,000-10,000 women enter prison already pregnant each year. Pregnant women are just not the visual that comes to mind when thinking about women behind bars.

One prison we visited, the Nebraska prison for women, is trying to address these issues head-on. When we arrived, the warden, John Dahm, escorted us inside the property. The first thing I noticed is that once we got past the gates and security the prison looked like a school campus. Within its confines, the minimum-security inmates are allowed to come and go to their scheduled classes and counseling programs. You can sense that the inmates are here, as the warden puts it, "As punishment, not for punishment." In other words, he focuses not just on retribution, but rehabilitation.

The prison also has a nursery. Seeing this, I had to keep reminding myself we were in a prison; at times, it seemed more like a halfway house or communal living situation for mothers and their newborns. The prison also has a flexible visitation policy for mothers with older children.

Deseray, an inmate in the general prison population, told us her 5-year-old son thought he was being punished because she was locked-up. She had to explain to him that, "No, mommy had done something wrong."

For those concerned about the future of Deseray's son, here's another disturbing statistic: According to Oregon's Correctional Department, a child with an incarcerated parent is five-to-six times more likely than other children to spend time in prison at some point in their lives.