You can't keep your little one from growing up too fast, but by filling a box with birthday mementos, you can at least capture a moment in time. Buy an acid-free photo-storage box (available at art-supply stores) to preserve pictures and cards, snippets of ribbon and wrapping paper, the invitation, candles, and more. Even better than a photograph, these keepsakes will recall the day in vivid detail; create a box to mark the first -- or every -- birthday.