Controls, variables and experimental replication are fundamental concepts in biology. Because of this, when we were building the content for our “Let’s Experiment: A Guide for Scientists Working at the Bench” course, we initially thought this would be fairly easy information to capture. But, as it often is in science, the reality is much more tricky. There are important nuances around what controls to do, what variables to pay attention to, and what different kinds of replication to do in the experiment (technical? biological?). Not to mention the question of how many times to repeat an experiment! Even coming up with solid definitions for these different concepts proved challenging to our expert speakers. It ended up being a really interesting part of our work to capture and convey the subtleties of these topics. We’re proud to release these videos from our course this week on YouTube (Module 2: Key Elements of Experimental Design), starting with the video “Experimental Variables: Keeping Track of Them All”.