What can truly melt your heart?

I mean we all go awww when we see a puppy dog fall over and look back with them big brown eyes. Or when someone posts a really lovely comment on Facebook or twitter to a friend or relative in need. But I think the one thing that really makes your heart melt is when a child makes a selfless gesture. I have two boys one aged twelve and the other eight. They fight and bicker like any other brothers but every now and then they have a moment. When one will show humility and a kindness that should not be in one so young. These moments make me smile and make my heart melt.

Do you have any moments of heart melting quality?