This talk describes the motivation for developing mathematical models, including models that are developed to avoid ethically difficult experiments.  Three different examples from the field of human health are presented. Jeffrey J. Heys is an assistant professor of chemical engineering at Montana State University. He received his B.S. in chemical engineering in 1996 from Montana State University, and his M.S. and Ph.D. from the University of Colorado at Boulder in 1998 and 2001,respectively.  His research area is computational transport and computational fluid dynamics in biological systems with an emphasis on fluid-structure interaction and multiphase flows. About TEDx, x = independently organized event In the spirit of ideas worth spreading, TEDx is a program of local, self-organized events that bring people together to share a TED-like experience. At a TEDx event, TEDTalks video and live speakers combine to spark deep discussion and connection in a small group. These local, self-organized events are branded TEDx, where x = independently organized TED event. The TED Conference provides general guidance for the TEDx program, but individual TEDx events are self-organized.* (*Subject to certain rules and regulations)