A recipe is a great way to learn about the procedure and the variables (or "ingredients") involved. Cookbooks are comforting and valuable: They're easy to follow, and people know what they'll get. The problem is that cookbook labs end just when things get interesting. The excitement of science is in understanding the discovery and pursuing the questions that arise--a reasonable definition of inquiry. Lab experiments fall on a spectrum from cookbook to open inquiry with guided inquiry somewhere in the middle. Experiments that progress from scaffolded to open investigations give the teacher a range of options and the student a path leading from a structured to a more adventurous experience. The best labs clearly define the procedure, include meaningful scientific content, and ask interesting questions. This article discusses four labs--centered on the science of heat transfer--that define the procedure, include meaningful scientific content, and ask interesting questions. The simple extensions described lead to more complex issues and opportunities for inquiry. (Contains 7 figures.)