For more information on what is Tekhelet, see our Tekhelet 101 Page. It is a clear and concise description of the mitzvah of tzizit and the obligation to place a blue string of dyed wool. This mitzvah was lost to Am Yisrael some 1300 years ago. Much information has been written on the topic of what is tekhelet. But along with many sources of information, Ptil Tekhelet aims to be the comprehensive source of information with our extensive and broad online library as well as our videos and and tying resources.