In an article, published today in Physical Review Letter, we demonstrate a new temperature record for image-current mediated sympathetic cooling of a single proton in a cryogenic Penning trap by laser-cooled beryllium ions. In our experiments we reach an axial mode temperature of 170 mK, corresponding to a 15-fold improvement compared to the best value achieved in previous experiments. Our cooling technique, which we have demonstrated with protons,  is actually applicable to any charged particle, so that the measurements presented in our new manuscript constitute a milestone toward the next generation of high-precision Penning-trap measurements with exotic particles, such as protons, highly-charged ions and antiprotons. The technique developed at BASE-Mainz has potential to be applied to antiproton-cooling at the BASE experiment at the AD/ELENA facility of CERN. .