This book evolved my understanding of proteins. They are actually sophisticated soft machines with specifically designed structures, and the design holds the mystery of life. The prion protein is a perfect example of such a design: replacing a few atoms of the protein can lead to dramatic and intriguing effects in the brain. While this phenomenon puzzled researchers for decades, molecular simulation opened a unique access to the mysterious design of proteins. It monitors the way the protein atoms move, interact and flex, even at any instance of time. With simulations we can “see” the fascinating atomic structure of proteins⎯ a unique view that I have enjoyed throughout the work. It was the colorful animation of the simulations that inspired me and led me to the secrets of the prion protein and the prion diseases. Are the simulations so realistic that they predict and explain the outcome of experiments? While I was finishing up this study, the announcement of the 2013 Nobel Prize of Chemistry excited the entire molecular simulation community. Simulations are realistic. Their power is recognized by the world!