  The production of mesons containing strangeness is studied using elementary
and heavy-ion probes with the FOPI detector at GSI-SIS. The observed inclusive
cross section of neutral kaons points to an in-medium modification in the
production. The momentum dependent ratio of cross sections of light and heavy
target nuclei turns out to be a sensitive observable for the in-medium
potential strength in transport codes. The experiments will continue studying
the production of charged kaons with elementary probes including the search for
deeply bound antikaon nuclear clusters in proton proton collisions.
