The nature of science (NOS) is an often neglected part of science teaching, yet it provides a vital background for students, detailing how science and scientists work and how scientific knowledge is created, validated, and influenced. Here, I review the concept of NOS and some of the challenges to its inclusion in science classes. In addition, I outline proposals, including those in the Next Generation Science Standards, for those aspects of NOS that should be featured in science classes. Finally, I discuss distinctions in NOS specific to the science of biology and conclude with some thoughts on how NOS can be incorporated into science instruction.