Opening with a very (very!) long mishnah on the 12 loaves of the shewbread, including their process and their location and their shaping and their measurements and their placement. Also, how some of that processing overrode Shabbat rules, and some did not. Rabbi Akiva’s general principle here is that if something can be done before Shabbat, it will not override the laws of Shabbat, but if it cannot be done before Shabbat (and not because a person ran out of time), those practices would override Shabbat. Plus, some of the comments of the Gemara – specifically on the way the shewbread was bent upwards but a significant measure, and set up on rods to allow the air to circulate and prevent mold.