"When looking at momentary impermanence on a gross level, we can see that a person changes from childhood to adulthood. One may think that there is continuity in the change that takes place. One may wonder when this change takes place and conclude that every year, everybody is different.

However, a change doesn't automatically take place at a certain point each year. One may conclude that every month, everybody is different, but the change doesn't automatically take place at a certain point in each month either. One may conclude that every day or every hour, everybody changes.

We follow this reasoning down to every single instant in which a change takes place, so there is impermanence in every instant. This is the subtle level of impermanence. It is easy to see changes that take place over the years, but, in fact, changes are taking place in every instant. Chandrakirti said that even a solid-looking diamond, which is as large as a boulder, changes every single instant."

Thrangu Rinpoche