In Rise of Cultures, the player can research various technologies. These are required to unlock buildings and infrastructure, units and features like Alliances, the Treasure Hunt and World Wonders. The most important thing about research is the progress through the ages. As soon as one has unlocked the first technology of a higher age, the player will progress to that age and upgrade the City Hall.
The Tech-Tree is a visual representation of the progress through the ages and technologies that one has researched and the ones that are yet to come. When hovering over a technology the blue arrow(-s) pointing away from the current technology are the ones that are unlocked after this technology is researched. The arrow(-s) pointing to the current technology are the ones that are required for beginning the research. Otherwise, it's marked as a blocked technology.
To unlock a technology the player has to first invest the needed amount of research points into it. When the bar showing the needed amount of research points is full, and the player has the necessary amount of resources the player can unlock the research. Research points requirements and resource requirements can always be fulfilled by using diamonds instead. When a technology is fully unlocked it gets marked in green.