The Buddha said that our six senses (eye, ear, nose, tongue, body, mind) and the six sense objects (sights, sounds, smells, tastes, touches, and ideas), are impermanent (Aniccā). What's important is to realize that impermanence.
When we look in the mirror, or see an old photograph of ourselves, we realize we are aging, that we are changing, that somehow our life is impermanent. The seasons, the weather, our possessions, our relationships - all demonstrate impermanence.
Life is not only impermanent, but that impermanence makes life imperfect, not quite right, and that generates suffering. And we suffer because we take things personally, because our strong sense of self creates attachment.
As we gain insight into the three I's, we realize that we are just energy flowing, without an unchanging subject of experience, just a focal point of fleeting moments of existence.