The Opposite of Matter?

Mothers: your body holds onto cells from your baby after you give birth. These cells pass through the placenta and some of them will wander through your bloodstream forever. One day, though, your little boy will come home from his dad’s house and tell you he’s a dog person now.
Some of his baby cells left inside you are stem cells and will help rebuild your body where it starts to break. Still, down the road, your teenage son will be the final person in your life to tire of going to the movie theater on time, as if there’s something wrong with sitting next to someone you love in the dark, waiting.
Some of his cells will travel to your brain and generate brand new neurons. Nevertheless, you will never get it right, the difference between dark matter and anti-matter, even though your son corrects you every time. You are clearly the only person in his world who can’t understand him. When you ask him to explain it again, he says one is matter. The other one is the opposite of that.
Your baby’s cells carry his father’s DNA. He’s inside you too. Mostly, that’s good or you, the variation, the teaming up to fight with many weapons, but stem cells can turn into anything. You never know their motives. Maybe they don’t even mean to gather right where you’re weak and turn everything right against you.