The technology tree, more commonly known as tech tree, shows available units, buildings, and technologies for a certain civilization in Age of Empires and Age of Empires II. Each civilization has its own unique technology tree. Unless the square All Techs is checked in the settings prior to the beginning of the game, only a limited number of units, buildings, and technologies are accessible for every civilization. However, doing so also eliminates civilization bonuses for every player.
Edit
Barracks
Blacksmith
Mill
