Getting students to think deeply about mathematical concepts is not an easy job, which is why we often use problem-solving tasks to engage students in higher-level mathematical thinking. Mathematical modeling, one of the mathematical practices found in the Common Core State Standards for Mathematics (CCSSM), is a type of problem solving that can allow students to think mathematically through realistic contexts. Modeling is also meant to help connect students to situations that resonate with their lives or the lives of others. A model-eliciting activity (MEA) is a useful tool for helping students develop and refi ne important mathematical concepts through realistic (and useful) contexts. What distinguishes MEAs from many other types of problem-solving tasks is that they are designed to allow students to bring their initial conceptions and ideas, which are likely in an early stage of development, to the problem to be solved. When students engage in these modeling tasks, rather than use mathematics that they have already mastered, they co-develop their mathematical ideas and their proficiency as problem solvers. The example provided in this article, Pelican Colonies MEA, shows how sixth-grade students' concepts of area developed through modeling. The authors describe strategies that can help students' conceptual development and ability to connect with other mathematical concepts.