My son, AKA My Favorite Domer, was home over Christmas, and once again I was struck by how fast he’s growing up.

It’s not just that he towers over me (though he does!). It’s not just that his voice is deeper, or his features more angular than rounded.

It’s his grownup demeanor — his sense of responsibility, his assuming ownership of his day-to-day activities, his maturity.

I’m thrilled, of course, that he’s finding his way. Making what I hope will be lifelong friends. Focusing on his future by tending to his present studies. Not procrastinating when it comes to undesirable tasks like term papers, when he’d rather be playing video games.

We were at Mass, and I caught myself looking at his hands, remembering the baby fingernails I used to trim. Those pudgy fingers now have lengthened into slender, artist/musician’s hands, set off by his Notre Dame class ring.

I looked at his sneaker-clad feet and was transported back to his infancy. When I took him in his carrier to my obstetrician’s office, everybody wanted to hold and kiss those soft little feet with the tiny, perfect toes.

I looked at his profile, the Roman nose of his Italian ancestors, the twinkling eyes and dark coloring of his Irish forebears. How fascinating to see the family traits come together in a unique way!

Now, all this looking happened in the space of just a few seconds. No young man wants his mom staring at him in public.

But after he goes to bed at night and is deep in sleep, I tiptoe to his door and stare.

Drink him right in. That’s a parent’s prerogative, you know.

It reminds me how fast time flies, from infant carriers and diapers, to Legos and school projects, to senior pictures and high school graduation.

Sure those young child days sometimes seem to last forever, especially when you are casually turned into a taxi service, a place for them to dump fears and worries, even a grocery store or fast food outlet. But those days just FLY by, really. Blink and before you know it, they’re grown and out of your house.

So may I make a suggestion — Enjoy every second with your precious offspring. When the going gets difficult (and it does, for all of us!), remember, This, too shall pass.

Does anything make a mom’s heart burst with love the way watching her sleeping “baby” does?

I think not.