The most perfect system ever designed is Human Body. It has to be perfect as it is not designed by humans but by God.
It is the duty of humans to maintain this body to be perfect till their final return to God. This is possible through proper diet and regular exercise.
Let us return back to our perfect system. We all know that liver do exist but starts functioning only when baby is born and drinks mother's milk or in unfortunate cases, other form of milk.
Let us consider ears now. They don't only allow you to hear but designed to carefully scrutinizing sounds and noises. During sleep, they allow only certain range of sounds and noises to wake you up. For e.g., soft music being played on radio will not wake you up but someone calling your name will do. This mean that ears listen to sounds of personal significance during sleep.
Amazing system!!!. God is Great.!!!