In this report we present new insights into the formation mechanism of Ag, Au and AgAu nanoparticles with alcohols, aldehydes and ketones in alkaline medium at room temperature. We selected methanol, ethanol, glycerol, formaldehyde, acetaldehyde and acetone to demonstrate their capability of reducing gold and silver ions under the above-mentioned conditions. We showed that the particles are also formed with potassium tert-butoxide in the absence of hydroxides. Our results strongly suggest that alkoxides, formed from any molecule containing a hydroxyl or a functional group capable of generating them in alkaline medium, are the actual and universal reducing agent of silver and gold ions, in opposition to the currently accepted mechanisms. The universality of the reaction mechanism proposed in this work may impact on the production of noble nanoparticles with simple chemicals normally found in standard laboratories.