In the human world, there is this technology called the virtual reality. I'm not sure when it started (at least the one with computers), but I guess it surfaced widely during the early 90's. The virtual reality basically puts you in a computer-generated world, making you think what you see and hear is real. It is limited to audio visual, though there are probably some machines that could generate physical contact to our body parts, utilizing little servos and prod sticks, imitating the virtual world. But hey, that's like cheating.
Little do we know however, that virtual reality exists in our body, in the form of emotions. It always amazes me how when your heart breaks, or gets wounded from emotional overwhelming, you can actually feel the pain physically. Funny how although there is no physical injury, the gaping wound inside feels real, and you even feel the blood slowly dripping. What's funnier is that the heart itself is virtual.
But what's worse is that unlike its machine counterpart, this one has no shutdown button.