This shiur is divided into two parts. The first half an hour of the shiur is an advanced in depth analysis of the Machlokes between Rashi and Tosafos as to he nature of Tashbisu and Bitul. The second half an hour of the shiur is based on an idea from Rav Shmuel Zucker as to why we are so makpid to remove even the smallest piece of chametz and to tell over the story of Yetzias Mitzrayim to even our smallest children.