This book contains contributions by colleagues, former students and friends of Professor Eli Reshotko in celebration of his 60th birthday. Since Professor Reshotko's scientific and engineering contributions have been in the areas of hydrodynamic stability, transition to turbulence, and boundary layer flows, it is only appropriate that the articles in this volume be devoted to these and related topics.<br/> The first two sections focus on instabilities and transition in subsonic and supersonic flows, respectively. The third section deals with developing turbulence, while the final section treats related problems in engineering fluid mechanics. The diversity and scope of the articles contained herein exemplify the insight and expertise required in the study of transitional and turbulent flows today -- traits which also exemplify Eli Reshotko's contributions to these fields. <br/>