With the current, very rigid tech tree we essentially have three sub "eras" for every game era made up of the columns of the tech tree. They are recognised by the game, even though their impact is very limited, for example some dynamic names depend on column instead of the current era. I was wondering if we could come with some informal names for those sub-eras. I propose the name "age" simply because it distinct from era and seems to work out well in practice. For example, for the first ten columns: - Stone Age - Copper Age - Bronze Age - Iron Age - Imperial Age - Late Antiquity - Early Middle Ages - High Middle Ages - Late Middle Ages - Age of Exploration Further ideas?