The nature of impermanence is not only seen in the grosser forms such as the death of every living being, the destruction of everything that is built up, and the dispersal of everything that is accumulated, but it is the pervasive nature of all phenomena in the world. Everything changes moment by moment, instant by instant. When we say a word, that word goes out and never returns again. It appears to be there, but when we try to hold onto it, it is already lost. All phenomena are of that nature, subtly changing from instant to instant. There is nothing that can abide, nothing in the world that has any stability or any ability to stay beyond an instant.

So all phenomena are said to be like a cloud in the sky that is constantly moving and changing, disappearing and reappearing, but never truly able to abide or hold its own nature. There is nothing in the world that can do that. So the world is said to be like a show with many different appearances and sounds, but with no stability or reality behind it. It's just a performance. Understanding impermanence in both its gross and subtle forms leads us to realise that the world is like a dream or an illusion.

-- His Holiness Kyabgon Chetsang Rinpoche