The Mishneh Torah was the Rambam's (Rabbi Moses ben Maimon) magnum opus, a work spanning hundreds of chapters and describing all of the laws mentioned in the Torah. To this day it is the only work that details all of Jewish observance, including those laws which are only applicable when the Holy Temple is in place. Participating in the one of the annual study cycles of these laws (3 chapters/day, 1 chapter/day, or Sefer Hamitzvot) is a way we can play a small but essential part in rebuilding the final Temple.