This chapter presents the task of judging bubble solutions to see which makes the biggest bubbles and the longest-lasting bubbles. Students design and carry out a scientific experiment to decide which bubble solution is better. This is a real challenge since something different happens every time and scientists often meet repeatability problems. When they do, they usually try to see the experiment from a new angle—for example, they might wonder if there are other ways to make bubbles. The chapter outlines three more challenges to designing good experiments.