Allowing students to create their own investigations and experiments to test hypotheses and answer essential questions is crucial to actively involving students in learning. It also provides them with opportunities to develop critical thinking and process skills. In this article, the authors explore a process called "BIDDI" ("Brainstorm, Investigate, Debrief, Debate, and Identify") that allows students to learn through doing. The BIDDI Process helps students take ownership of their education while learning about porosity, permeability, and settling rates. This activity, "It's All in the Particle Size," not only helps students learn about sedimentation, but it also helps them become independent thinkers, learners, and doers. This activity has three parts that each take approximately 90 minutes: (1) Brainstorm and plan investigation; (2) Set up and conduct 1-2 investigations; and (3) Conduct remaining investigation, and if extra time is available, conduct the debrief-debate-identify segments. (Contains 5 figures and 2 online resources.)