There’s a picture of my two sons hanging on the wall at the top of the stairs, just outside their bedroom. They’re both wearing Bears jerseys, and they have their arms around each other. They look so genuinely happy that I smile just thinking about it. The picture was taken in April 2009, when my older son was four-and-a-half and my younger son was almost three.It might as well have been taken yesterday for how vividly I recall seeing it for the first time.They share a bedroom, and when I tuck them in at night I look at that picture. On the two flights of steps up to the bedroom, we’ve got at least a hundred photos of the kids and our family in collage frames. Sometimes I take my time as I go up or down the stairs and look at the pictures showing trips to the park, vacations, silly moments, special holidays, or just an instant in time that my wife had the talent and foresight to capture for eternity.And I can’t believe it’s 2016.Wasn’t it just yesterday that my youngest daughter ripped my wife’s earrings out of her ears when I picked the two of them up for our first date?How have almost eleven years passed since we worried as my older son had surgery when he was three weeks old?I can still feel the cold, wet dew on my feet as I scrambled out the front door without shoes on in the middle of the night when my younger son was born.And I think I’m still smiling from the swiftness with which my youngest daughter began chewing on her hand the moment she entered the world.Yet years have passed since all of these things happened. Thousands of days. And despite my best efforts to slow down and appreciate every day, it still seems like it’s all gone too fast.A video on Facebook drove this point home this morning. It showed the different phases of a young girl’s life. It shows her interests, her style, her friends, the ways that she changes over the years. It captures a feeling to which every parent can relate and appreciate. The video is very well done, but its true impact comes when you substitute the girl in the video with your own child or children. (Note: I borrowed the title of this post from that video.)It conjures the same feelings that arise during the montage of Jessie’s owner growing up in Toy Story 2, or when Andy goes away to college and leaves his toys with a little girl in Toy Story 3.It’s the feeling that childhood is a phase. But it’s not just one phase, it’s a series of phases, some overlapping, some leading into the next. And the beautiful heartache of watching our children grow and learn and mature while we realize that when these moments are gone, they’re gone. And sometimes we don’t even know a phase is near the end until well after it’s over.Other than birthdays, or last days of school, or new years, or other calendar markers, there’s almost nothing that tells us when a phase is over or a new one begins.One day my older daughter just stopped pronouncing hamburger as “hambahder”. She liked cats. She hissed like a cat. She liked frogs. She sewed. She liked hippie stuff. She liked Hannah Montana. She liked Twilight. She liked The Fault in our Stars. She graduated high school.My older son had meaty drumsticks. He liked Elmo. He’d repeat in a whisper words that he heard. He slept with a cuddle blanket. He loved flags. He loved sea creatures. He liked Handy Manny. He liked Super Mario. He played soccer. He played baseball. He took swimming lessons. He liked Minecraft.My younger son didn’t like me for the first nine months of his life. He had very straight hair. He’d act out scenes from Toy Story. He was obsessed with Caillou. He took swimming lessons. He played baseball. He wore an eye patch. He did planks all the time. He counts steps on a Fitbit.My youngest daughter wore cloth diapers. She had very dark hair. She repeated the same two sentences once a day for well over a year (“Remember when that dinosaur spit on mama’s camera yesterday? That was so funny.”) My wife took at least one picture of her every single day for the first couple years of her life. She took ballet. She likes Caillou. She says “Chicken butt.” She’s a vegetarian (except for pepperoni).These are things that we’ll remember about their childhood. The phases of their lives. Some continue, most are over. Those phases, along with all the moments captured in the hundreds of thousands of pictures my wife has taken, and the books we’ve read, and the movies we’ve watched, and the places we’ve gone, and the zoos and parks and museums we’ve visited, are the stuff memories are made of. The stuff life is made of. It’s why I tuck my kids into bed every night, and why my wife bakes with them, and runs with them, and paints their nails, and celebrates days like National Chocolate Cake Day.In my house we have a couple of tangible things that have marked the phases of childhood. There’s one bedroom that each of the four kids have called their own at one time or another. It was pink when we built the house, then we painted it yellow, and now it’s purple. And there’s a spot beneath the window, right up next to the trim—you have to get down on the floor and look up to see it—where you can see all three paint colors. And that one section of wall reflects the phases of childhood.We also have a wall in a closet in the basement in which we’ve measured the kids every few months for the past ten years. We began when my oldest son was about a year old, and continued as all four kids have grown. There are dozens of marks on the wall, each with an accompanying name and date. If anyone ever painted over that wall I’d cry for months.Childhood is a series of phases. But that wall better be like the memories we’ve created: Forever.So pay attention. Get involved. They're your kids, and they're only this age once. There are no do-overs. Live this phase. No matter what it is.Because tomorrow it might be gone.IF YOU LIKED THIS POST I BET YOU'LL ALSO LIKE: The 939 Saturdays of ChildhoodPREVIOUS POST: We Can Do Better Than Donald Trump, Can't We?Want an e-mail every time I write something new? Type your email address in the box and click the "create subscription" button. 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