Sometimes, when the kids are sitting with me watching videos, reading a book or chatting about life, I find myself giving their heads a sniff. Just like when they were tiny babies.
Maybe it's one of those endorphin or oxytocin things, but it's mostly a habit that lets me "take in the moment", so to speak, so I can remember later how small they once were and bask in how thankful I am to have these little guys in my life.
(Of course, I have other people I am also thankful for... Hubs, my parents, my siblings, friends... but I generally don't sniff their heads.)