A critical investigation of the source of techeiles, its disappearance, and the modern murex theory. What is the chilazon? Why is it so important? Do we have it today? This sefer presents a comprehensive overview of the chilazon, the source of the long-lost techeiles. What are its halachic parameters? Where was it found, and why did it disappear? Can it be rediscovered today? These questions and more are addressed clearly and in an organized manner. In particular, this sefer critically reexamines the possibility of the murex trunculus as a candidate. You have tackled a broad and complex issue and successfully present it in a clear and organized fashion, showing the sources from Chazal down to the controversies of today. -Rav Reuven Feinstein, Rosh Hayeshiva, Mesivta Tiferes Yerushalayim By Rabbi Mordechai Cohen