STEM is a commonly used acronym in today's education world. Parents hear the term and hope their child's school will be embracing it, teachers plan units encompassing it, even those outside the education realm have heard it and think it is important. But, do students actually understand the four disciplines and can they clearly express what they are learning about: Science, Technology, Engineering, or Math? Through this unit developed for an upper elementary classroom, students are guided through the four STEM disciplines in a personalized learning experience about the general theme of humans' impacts on Earth and a specific place-based project on the use and disposal of plastic water bottles in the school. This unit provides students with opportunities to observe the school, investigate the natural world, manage constraints, and act on driving questions that motivated them individually to promote positive change. STEM is becoming more prominent in schools across the world, making sure students understand the disciplines is the first step to having a successful STEM education program. [For a related article, "Plastic Pollution to Solution," see EJ1172596.]