Tribology is the unfamous science of how dry and lubricated parts interact with each other. Understanding it plays a key role in keeping today’s machinery in reliable and efficient operation. Although tribology as a research field has progressed a lot in recent decades, modern machinery is even more demanding, and it further pushes the boundaries of reliability in the ongoing quest for higher efficiency and productivity. This book is dedicated to this quest and shall represent the current state-of-the-art research in tribology covering many different applications ranging from machine elements, as they are used in a vast range of industries, to understanding more about today’s advanced lubricants, materials, and coatings. Finally, the scope of this book is not limited to the more traditional approaches used in tribology research but also seeks to cover the most recent advances in the field of data science and machine learning, which are aimed to expand the understanding of tribological phenomena, predict and optimize them, and ultimately to apply this knowledge to real-time monitoring of tribological mechanisms and to make maintenance more predictable.