Why do they grow up so fast!

It seems as only yesterday my sons were babies! They have grown up too fast!!! This fact was pinted out to me last night by my ODS. During the summer he was just below my chin, but as he showed me yesterday - he is now up to my lips!! He joked that, "Well now you don't have to bend down to kiss me." It made me realize that before to long, he will be the one bending down!