We live in a world teeming with microbes. One of the most influential areas of modern biomedical science is elucidating the ramifications and complexity of host-microbe interactions that affect animal and plant health, and dramatically influence micro- and macro-ecosystems. Fueled by technological advances, we are entering a new era of interdisciplinary approaches that enable investigators to delve deeply into the reciprocal influence of host and microbes. Training new scientists in this area will fill an unmet potential for UC Davis graduate education. The DE-HMI will synergize the campus' scholarly power to train scientific leaders that will drive new technological transformation both in the academic and private sector arenas. In addition, training students to work within an arena of interdisciplinary investigation will enable them to tackle pressing and difficult problems that they will encounter throughout their scientific careers. The DE-HMI will train students with various backgrounds to engage in science that requires a multidisciplinary approach. No graduate program at UC Davis provides the necessary educational background to enable students to rigorously investigate the complex mechanisms that underlie host-microbe interaction. The DE-HMI fills that need.