Until about two decades ago, the standard method of studying a microbe was to isolate it, grow it in culture, stain it, and examine it under a microscope. Today, new genomic tools are helping expand our view of the microbial world. Instead of viewing them as “germs” to be eliminated, we are beginning to perceive our microbes as an extension of ourselves — an important organ with unique functions essential to our well-being. Scientists even came up with a new term, “microbiome,” to define our microbes' genes as an important counterpart to our human genome. With new information about the human microbiome comes the challenge of shifting biology students' focus from casting microbes as pathogens toward appreciating microbes as symbionts. “The Human Microbiome,” a curriculum supplement produced by the Genetic Science Learning Center, emphasizes that microbes living in and on our bodies perform neutral and beneficial functions, that human microbiota form thriving ecosystems, and that disruptions to our microbial ecosystems may have consequences. In this article, we describe the curriculum materials, provide strategies for incorporating this cutting-edge topic into biology classrooms, list connections to the Next Generation Science Standards, and report on recent research testing the curriculum supplement's effectiveness for student learning.