There is a lot of talk these days about corporate social responsibility and ethical supply chains. But monitoring the entire supply chain, especially in China's domestic market is almost impossible. In the neighborhood surrounding labor organizer Zhang Zhiru's office in Shenzhen's Bao'an district, every second building seems to host a "black factory," a small illegal workshop where migrant workers punch out individual components of larger products. The shops in this neighborhood specialize in the plastic shells for cell phones. While black factories provide a lot of informal employment in this neighborhood, they also have a dark side. Because they are at the bottom of the supply chain, they often skimp on safety to save money. The result, as these pictures show, is a work environment where injuries are common. Because these factories don't actually exist on paper, it's almost impossible to hold them accountable.