This past weekend — at just shy of 9 months of age — Aerin finally sprouted her first two teeth. As I proudly ran my finger over Aerin's new incisors (and got repeatedly bitten in the process, as having her mother's finger shoved in her mouth is something that she obviously does not like), I couldn't help but think back to when Claire got her first teeth at 6 months of age. I had expected Aerin to get her first teeth at approximately the same age too, so the 3-month difference — which is quite large in a baby time — was yet another evidence of how differently my daughters grow, develop, and become themselves. One of the things I find most difficult...