With my son's fourth birthday came our household's first set of real Legos. (Thanks, Grandma!) He plays with them almost every day, as does my daughter. I'm sure we have many happy hours of building ahead of us. Stashing the Duplos in the closet made me nostalgic though. So, before they disappear into the box marked "toddler toys", let me write a little tribute to the good they've done for us.