Each recipe in this book has been tested and retested several times to ensure that you end up with a creation resembling what is depicted in the photographs. Sometimes, though, things happen, and it might not quite work out the way you were envisioning. Why? Well, if you recall science from grade school, it is possible that your independent, dependent, and controlled variables might be slightly off. It really depends on the recipe before you. Sometimes humidity or altitude cause slightly different results. Other times your leavening agents may not have been fresh. If you substituted ingredients such as eggs, that could have been the pitfall. Did you use the right ingredients, and did you measure correctly? Did you overmix the batter? Did you add the ingredients in the right sequence? Was your oven temperature correct? Did you use an oven thermometer? Did you open the oven door while your cake was baking? Did you wait long enough? Did you use parchment paper to line your cookie tray? As you can see, there are countless possibilities for what could have gone wrong. Baking, like anything, takes practice.