Instinct is perhaps the most amazing phenomenon in nature, as it is what inspires animals to perform the most complex tasks with unparalleled agility, skill, and precision. It comes spontaneously, without training, experience with it, or guidance from the centers of mental powers. A bird, for example, builds its nest according to the model followed by its fathers. For thousands of years without anyone getting used to it or seeing for themselves the way it was built, this nest may be a den in a tree trunk, as the owl does, or a house made of grass, moss, and tree leaves, as the owl does. Abu Fasada, the silkworm weaves silk threads around itself when it reaches a certain point in its growth, so that if its work is interrupted, it cannot begin again and dies without completing its development cycle.