It was 130 degrees when I was first introduced to the brick kilns of Nepal. In these severe temperatures, men, women, and children -- whole families, in fact -- were surrounded by a dense cloud of dust while mechanically stacking bricks on their heads, carrying them, 18 at a time, from the scorching kilns to trucks hundreds of yards away. These are slaves. Deadened by monotony and exhaustion, they worked without speaking, repeating the same task 16 hours a day. They took no rest for food or water, no bathroom breaks — although their dehydration suppressed their need to urinate.

Around the world human traffickers trick many people into slavery by false promises of good jobs or good education, only to find themselves forced to work without pay, under the threat of violence. Trapped by phony debt, these slaves are hunted by local police and private security guards if they try to escape. Sometimes slaves don't even understand that they're enslaved, despite people working 16 or 17 hours a day with no pay. They're simply used to it as something they've been doing their whole lives. Their bodies grow weak and vulnerable to disease, but they have nothing to compare their experience to.

For the last 28 years I have documented people in more than 100 countries on six continents. In 2009, at the Vancouver Peace Summit, I met a supporter of Free the Slaves, an NGO dedicated to eradicating modern-day slavery; weeks later, I flew down to Los Angeles and met with the director of Free the Slaves; thus began my journey into exploring modern-day slavery.

Oddly, I'd been to most of the locations where I started photographing slavery many times before. I even considered some of them homes-away-from-home. But there can be dark corners in familiar places.

These are not images of "problems." They're images of people. There are 27 million slaves in the world today: That's more than double the number of people taken from Africa during the entire transatlantic slave trade. A hundred and fifty years ago, an average agricultural slave cost over three times the average yearly wage of an American worker, about US$50,000 in today's money. Yet now, entire families can be enslaved for generations over a debt as small as $18. Slavery is illegal everywhere, but it exists all over the world. — Lisa Kristine

THESE MATERIALS WERE PREVIOUSLY PUBLISHED IN THE ATLANTIC.

Lisa is a humanitarian photographer who specializes in images of remote Indigenous cultures. Lisa's most recent focus has been documenting modern day slavery and collaborating with NGOs in this effort. By purchasing one of her prints or slavery book or soon-to-be poster a percentage of proceeds will go toward fighting slavery. Her work may be found at www.lisakristine.com.