This book is a tribute to the achievements of Ilya Spitkovsky in operator theory, pseudo-differential and integral equations, factorization theory and many other related topics. Ilya Spitkovsky started his career under the guidance of Mark Krein in Odessa, Ukraine. During these years, Ilya's rigorous and clear style of doing mathematics matured. Since 1990 Ilya Spitkovsky has been a professor of mathematics at the College of William and Mary in Williamsburg, Virginia, where he has taught a wide range of courses, including linear algebra, real, complex, and functional analysis. He has authored more than 300 publications, including four research monographs, and edited eight books of proceedings. Ilya Spitkovsky is currently a member of the editorial board of five international journals. Since 2013 he is a professor of the Division of Science and Mathematics New York University Abu Dhabi, UAE. With this volume, the authors of the articles join the large family of people who congratulate Ilya Spitkovsky on his anniversary. It is their wish that the contributions in this volume offer inspiring insights to researchers working in these fields.