The goal of the book is to provide a simple and conceptually intuitive introduction to nonlinear spectroscopy via the formalism of quantum processes and wavepacket dynamics. Through this unified framework, the authors provide t simple analytical models, examples, and concepts to understand the workings of nonlinear spectroscopy in depth. This book provides an introduction to the field for advanced undergraduate, graduate students, and researchers, in a simple and pedagogical manner. It will also be useful for practitioners who are already familiar with the subject, but who want to develop a more conceptual understanding of it.