The Grimms published the first volume of their collected folk tales -- called "Children's and Household Tales" -- in 1812, and a second volume in 1814. Though they continued to write scholarly books and articles on linguistics and medieval studies, their folk tales gained them the most recognition, and they even received honorary doctorates from their alma mater.
By the way, if you've ever read "Grimm's Fairy Tales" and felt they were a little dark for kids, you have German culture during the early 1800s to thank. After the book was published it attracted criticism for its sexual content, so the brothers edited these themes out of subsequent editions. But because the violence of the stories wasn't frowned upon in the same way, it was retained and in some cases even increased.
In 1825 Wilhelm married Henriette Wild, whose family had supplied the Grimm brothers with some of the best stories for their folk tale collection. Jacob never married, but apparently lived happily with the new couple -- one scholar noted that the brothers "both live[d] in the same house, and in such harmony and community that one might almost imagine the children were common property." The brothers moved to Gottingen in 1830, where they established the field of Germanic studies at the University of Gottingen and continued to publish books on mythology and linguistics, while simultaneously editing their collection of folk tales.