Organic/inorganic hybrid nanocomposites, in particular polymer based hybrid nanocomposites, constitute emerging advanced materials since they combine unique properties from the inorganic and organic (i. e. polymeric) components. We investigated three different hybrid nanocomposites depending on dimensions of the dispersed phase in the nanometer range,; polymer-layered silicate (PLS) nanocomposites where polymers are mixed with layered silicates, polymer/graphene oxide hybrid nanocomposites, and polymer hybrid nanocomposites with reinforcing polymers with isodimensional phases of inorganic silicas using sol-gel reactions. This Accounts reports the chronological progress of our landmark results on the polymer based hybrid nanocomposites of the three characteristic types that have been prepared in my laboratory for more than two decades, with their impacts, importance and advanced application of the related research fields for readers.