Sometimes I still can't believe that our oldest son is the father of twin baby girls. And identical ones, at that. Identical twins are created when a fertilized egg splits in half, resulting in two exact copies of the original. How amazing is that? As if the creation of one tiny human life isn't miraculous enough! And what are the odds? Actually, writing that question made me curious, so I just took a quick break to look it up on-line; and apparently, the odds of having identical twins are about 1 in 250. That's only a 0.4% chance, but still, I was a bit surprised by that. I thought they'd be about 1 in 1,000.
My twin granddaughters have identical DNA fingerprints, but here's another little factoid that I learned during my research: identical twins don't have the same fingerprints. The arches, loops, and whorls that form on the fingertips result from different environmental factors, such as womb pressure and contact with amniotic fluid; so no two people on earth share the same prints, not even identical twins.
Along with different fingerprints, identical twins also have different personalities (my son and his wife have already commented on these differences with their babies); this is because early in their development, environmental factors and external influences in the womb can change the personality--and even the appearance--of twins. It's obvious that whatever goes on inside the womb as twin babies are growing and developing can result in differences in appearance: my little granddaughters are easy to distinguish from one another (at least so far) because one was more than a pound bigger than the other at birth--and she continues to outweigh her sister. But hey, what happens in the womb, stays in the womb. :)
It is a miracle that we have two little girls in our family now, after being an all-male household for so many years. But it's even more miraculous that they are identical twin girls!