Who is a minor? The Gemara follows the mishnah's discussion of the abilities of the child - to ride on his father's shoulders to the Temple, or to walk holding his hand. But how did the child get to Jerusalem to begin with? Clearly, his mother brought him, as she comes to Jerusalem to fulfill her own obligation of simcha, rejoicing. With support for this presumption in the biblical story of Chana and Shmuel. And the Gemara then extrapolates to connect children's obligation and exemption to that of adults. Also, explaining the dispute in the mishnah between Beit Hillel and Beit Shammai regarding the expense of each sacrifice by understanding their fundamentally different approaches to the nature of korbanot, and the "original" sacrifice. Plus, a dispute between R. Yishmael and R. Akiva that unpacks the original dispute even more fundamentally.