Can you really make edible building blocks? Yes! They're pretty, fun, and require no specialized skills (unless you count heating and pouring). They're a great rainy day activity, and they make really fun party favors. The biggest challenge is keeping them uneaten long enough to play with them!
You'll want everything handy before you start. For blocks, you can use cube-shaped candy molds or just an ice cube tray. (Keep in mind that the molds we used make 2- and 4- oz. cubes, while standard ice cube trays make 1-oz. cubes.) You'll need at least one 3-oz. package of Jello and 2 small unflavored gelatin packets per color. (For 6-oz. packages of Jello, you'll need to use 4 gelatin packets.) If you're using a silicone tray, you may want to set it on a baking sheet so it's easy to move once it's full of hot gelatin.
Carefully place your mold in the refrigerator. Refrigerate until completely cold and set, about an hour.
Grown-up step: To unmold, very carefully pry the blocks out with a toothpick or butter knife. (Don't worry -- they're much sturdier than they look.)
If desired, dust the bottoms lightly with cornstarch or powdered sugar so they don't stick together when you stack them.