Belgrade -- more vulnerable than adults, exposed to smugglers and violence, and they do not know how to protect themselves - children make up a third of the refugees seeking their way to Europe.

The most vulnerable among them are those who are travelling without their parents, usually in a group of peers or accompanied by unknown people.

Speaking about human trafficking is somehow surreal. It feels like talking about horror movies, but it is a sad reality for thousands of people. According to a UN report published last year, from 2010 and 2012, 510 human trafficking routes around the world and victims from 152 countries were detected.