Big Day

Ok, maybe there was nothing earth shattering about our day yesterday, but I felt like I should document it. Sydney is growing up SO FAST and yesterday she seemed very big all of a sudden.
First of all, after her morning nap, she walked down the stairs with me, holding on to the wall and my hand. Syd usually does really well going up and down the stairs, but we've always encouraged her to scoot down on her booty or slide down on her tummy. I guess her legs weren't long enough before now either! Boy, did she look like a big girl walking down with me.
When she got dressed after she woke up from her morning nap, the only thing she lacked was a bow in her hair. We came downstairs, and there was a bow on the coffee table. As soon as she saw it, Syd went and grabbed it and brought it to me, holding it to her head. Yay!! I was so proud!! (I know, this is a silly thing to get excited over, but I love that in spite of her tomboy-ish attitude toward climbing, she's still a girly girl)
Later in the afternoon, we took a short trip to Target to pick up a few things. I guess with her sitting in the cart I was able to see her from a different angle. While she was playing telephone with a pair of sunglasses we had picked up for her in the dollar section, she opened her mouth wide as she said loudly into the glasses, "HI!" I happened to notice a new tooth-- a molar back in the back on her right side. I figured she'd been teething (she's been biting a lot, and drooling like crazy), but I had found another new tooth on Tuesday and assumed that was it. Standing there in the middle of the store, I reached my index finger into her mouth and felt a few more tiny prongs above the molar too! What in the world?! Two molars in one day??  No wonder she's been trying to chew everything!
As if that wasn't enough in one day, while she was playing before her afternoon nap I was sitting on the couch checking my email. She came over to me, tugging at her diaper. My nose let me know it was time to change her! I asked, "Do you need a new diaper?" Syd's reply? She walked back over to her play area, picked up a diaper out of the basket, and sat down on the floor where I usually change her! I knew she didn't like being dirty, but that was definitely the first time she came to "tell" me she was ready to be changed. 
Who is this big girl, and what happened to my tiny baby? Someone told me just yesterday that Sydney will seem even bigger come September when we bring a new baby home. I'm prepared for that, but I'm afraid my girl isn't waiting around!