For kids: Build a blown glass ornament collection year by year

Since my son was born I've bought him a new painted blown glass ornament every year. They all relate somehow to the year that's ending - his favorite food, a place we've visited, or something else that reminds me of him at this specific age. I add a small paper tag with the year written on it. When he grows up and has his own Christmas tree, he'll get the whole lot, and because I stick with blown glass they all fit together as a collection despite being a variety of things.