In this course, we concluded with a unit covering the immunity within the body’s mucosa and skin. Here, we discussed the nature of intestinal immunity, specifically how the body’s natural gut mucosa is not only home to 50 trillion lymphocytes, but host to over some 30 trillion commensal bacteria. These bacteria, which form a microbiome, stimulate and maintain the body’s tolerance to itself mainly through their influence on the development of T_REGs. Such an elementary understanding on the microbiology of the intestine connects to my interest in medical lab sciences, especially concerning cultures of fecal samples or intestinal tissue; I found both the population and demographics (so to speak) of the commensal microbes surprising, as I had previously underestimated both the size and variety. This unit specifically widened my perspective on the amount of “safe” bacteria that live both in and around us, and demonstrated just how much of ourselves aren’t really “us”!