Tribute to Ronald Brown, 1935 - 2024

Dear Ronnie,

I am one of many who will always remember your mathematics, your kindness, and your friendship, and who will greatly miss you. Among other things, you created a new mathematics between category theory and topology, with groupoids and higher groupoids playing a special role in it, which is certainly appreciated but not yet fully understood…
I remember all your kind invitations to Bangor, and I am very glad we published four joint papers. I am very glad Maria Manuel Clementino, Marino Gran, Timothy Porter and I edited a special volume of JHRS dedicated to you for your 80th birthday. 

George Janelidze.