Earlier this year, our dear friend and colleague Pieter Hofstra (1975-2022) passed away. Pieter obtained his PhD from Utrecht University, under Jaap van Oosten, studying realizability toposes. His research interests included general topos theory, realizability, inverse semigroups and groupoids, abstract computability, and homotopy type theory. Among his recent works, with J. Funk, he introduced the notion of isotropy groups of toposes, which he was actively developing with students and colleagues. While Pieter was a brilliant researcher, a kind teacher and a caring supervisor, we will most remember him as a friend. Today we (RB, Eugenia Cheng, Robin Cockett and Phil Scott) announce that the journal Theory and Applications of Categories, a journal for which Pieter was an editor, will dedicate a special volume in his honor. Authors are invited to submit their manuscripts in electronic form to Richard Blute rblute@uottawa.ca, possibly suggesting one of the Guest Editors to be assigned to their paper. All papers will be carefully refereed following the standards of "Theory and Applications of Categories". Prospective authors are requested to: 1. Copy the managing editor of TAC, Geoffrey Cruttwell (at tac@mta.ca), when submitting an article. 2. As with ordinary TAC papers, for the final version, authors should follow the instructions on the TAC website and then send their final .tex and .pdf files to Geoff (again at tac@mta.ca). The guest editors would much prefer that also the initial submission of a PDF already use the TAC template to simplify the work of reviewing. The deadline for submission of papers is May 31, 2023. The Guest Editors Richard Blute Eugenia Cheng Robin Cockett Philip Scott [For admin and other information see: http://www.mta.ca/~cat-dist/ ]