When you want to enter the US, you get processed by the US-VISIT system. Two fingerprints and a photo are taken from you. From my view, it´s something like a accounting system for visitors. To state it simple: you check in to the US and you check out of the US. In principle you know, how many and which visitors are in the country. Sounds good. But in fact, the reality isn´t always cute to such simple thoughts: In an report of the Government Accountability Office several problems with this system were reported, ranging from organisatorical and technological problems with it. My personal conclusions from this story: