I will discuss (a few aspects of) origins of bisimulation and
bisimilarity, in the three fields where they have been independently
discovered: Computer Science, Modal Logic, Set Theory.
Bisimulation and bisimilarity are coinductive notions, and as such
intimately related to fixed points. Therefore I will also present some
some historical remarks on coinduction and fixed points.
Finally, if there is time, I will present some problems for future work,
that have to do with enhancing the bisimulation proof method.