With the supporting feedback received over these years after the first edition, the goal of the second edition of this book inherits the same as the first edition. The first is to facilitate the understanding of crystallization fundamental properties and the impact of these properties on crystallization process development. The second is to improve problem solving ability through actual industrial examples under real process constraints.

In the second edition, the fundamental knowledges and key examples from the first edition are retained. New learnings are incorporated to reflect the current practice and potential future direction. These include a deeper knowledge on the phase behavior between drugs and solvents/excipients and in silico solubility prediction and screening (Chapter 2); formation of stable/metastable polymorphs via equilibrium and kinetic factors and conformer screening of salt/cocrystal and chiral resolution (Chapter 3); in situ seed generation via wet mill, model‐based crystal growth/nucleation parameter estimation, and process optimization (Chapter 4); CFD simulation, mixing scale‐up, and quality‐by‐design/process control strategy (Chapters 5 and 6); updated examples of anti‐solvent/evaporation/reactive crystallization (Chapters 8, 9, and 10); and API/excipient coprocessing of amorphous and crystalline solid dispersion composite (Chapter 13). Additionally, in the second edition, new chapters on filtration and drying downstream operations (Chapters 11 and 12) are added to address the final isolation aspects of solid properties after the crystallization.

During the period in preparing the second edition, two of our authors, Drs. Ed Paul and Mike Midler, passed away. However, their passion and dedication will continue to stay through this book.

Finally, as cited in the first edition, Matthew: 12:33, “Either declare the tree good and its fruit is good, or declare the tree rotten and its fruit is rotten, for a tree is known by its fruit.” It continues to be our hope that you, as readers, will find the second edition of this book useful for your works. If so, this will be the nicest reward for us.