Vista - How triggers work? Is there any way to listen PropertyChange

Dear all

I know I can add trigger in XAML or code
such as <Trigger Property="IsMouseMover" Value="True">

And do some actions or setter while the conditions of triggers happens.
So I assume triggers can listen some property change and do some
corresponding actions.

And somtimes I want to acheive something. I have to listen some
property change like trigger. But I have no idea about how to listen
them

For example, I want to listen Panel.Children's Change.
Is there anyway to listen dependency properties change?

Thanks
Have a nice Day

HolaMan