Schematic depiction of the key experiments described in the text where the experimental controls failed. The experimental treatments or the lack thereof are indicated on the top of each arrow. Top part of each panel depicts the actual experiment and its result. Bottom part of each panel depicts the failed control experiment (bold). The grey shaded box shows the expected result. On the left part of the red shaded box the actually obtained result is shown, whereas on the right part of the red shaded box the unexpected discovery, that was triggered by the failed control, is indicated in bold letters.