At any given moment, about 15,000 men and women are living in solitary confinement in the federal prison system, housed in tiny cells not much larger than a king-sized bed.
"It is hard to describe in words what such a small space begins to look like, feel like and smell like when someone is required to live virtually their entire life in it," says Craig Haney, a psychologist at the University of California, Santa Cruz.
But Tuesday, Haney, who has studied life inside prisons for three decades, had an opportunity to paint that picture.
I'm Michel Martin and this is TELL ME MORE from NPR News. They say it takes a village to raise a child, but maybe you just need a few moms and dads in your corner. Every week, we check in with a diverse group of parents for their common sense and savvy parenting advice.
I've never in my life desired a low-sodium biscuit, but I let the well-groomed woman at the Fancy Food Show in Washington, D.C. this week goad me into eating one.
"They're soooo good, I swear," she says.
It's perfectly fluffy and edible, this low-sodium biscuit, but seconds after it's gone I'm regretting having just wolfed down the whole thing. That's precious space in my stomach that I've just forfeited for an unremarkable food I'd never be interested in eating again.