Make: Online guest author Tito Jankowski found these gel electrophoresis cookies from last year on Not So Humble Pie.

Using your purple icing, pipe a square outline on each of the cookies and allowed it to set. Given the consistency of your icing should take at least 10 minutes, probably longer. Then thin the remaining purple icing with a little bit of water and flood each of the squares. Before the purple icing has set, use the pink icing to pipe in the little lines to create the markers.

Allow the cookies to dry overnight.