In honour of Bob Madix's enormous contributions to the field of surface reactivity we here report work on one of the reaction systems he pioneered, namely, the adsorption and reaction of methanol and formic acid with oxygen on Cu(110). We will report mainly STM and molecular beam results which show that the active site concept depends (of course) on the reaction used. Here the active oxygens for methanol reaction (oxygen island edge sites) are shown to be different from those for formic acid reaction (all sites). The beauty of nature at the ultra-nanoscale is revealed by STM, just as it is by our eyes for the world around us.