As you enter the Classical Age, you will be able to build a Library which will allow you to select a few Technology aspects which will help your city and Army grow. The focus of these Technology are vast--ranging from gathering and even up to engineering and defense.
Each Technology shall have three chapters available. Of course researching a certain Technology would require a payment and that payment can come in the form of Food or Gold. In the beginning, each Technology would only cost 50,000 Food. Once you will decide to upgrade, then the price will be higher--sometimes doubled too.
There is a total of 32 Technologies to research--which are categorized into six levels. These levels shall depend on the level of your Library so in order to research on more advanced Technologies, be sure to level up your Library often.
Also, when picking out which Technology to research, make sure to think about what aspect in your city you would like to focus on--growth or defense--so your resources will be allocated properly.
Level 1
Pottery
Chapter 1: Increases resources from Fruit Trees and Gold Mines
Chapter 2: Increases chance of finder Cider and Metal by 10%
Chapter 3: Increases Fruit Tree limit by 2
Roadways
Chapter 1: Increases Road limit by 5%
Chapter 2: Increases Road income by 10%
Chapter 3: Increases Road limit by 5
Reinforcements
Chapter 1: Provides hidden defenders from the forest
Chapter 2: Increases defender attack by 10%
Chapter 3: Provides more hidden defenders from the forest
Free Companies
Chapter 1: Increases Mercenary health by 10%
Chapter 2: Increases Mercenary attack strength by 10%
Chapter 3: Increases Mercenary Army limit by 1
Exploration
Chapter 1: Refunds 10% of the cost to clear forests
Chapter 2: Decreases cost of debris clearing by 50%
Chapter 3: Have a 5% chance to find an animal when clearing debris
Watch Towers
Chapter 1: Increases Tower limit by 1
Chapter 2: Increases Tower health by 10%
Chapter 3: Increases Tower attack by 10%
Machinery
Chapter 1: Increases Catapult attack by 10%
Chapter 2: Increases Catapult health by 10%
Chapter 3: Increases Catapult limit by 1
Cast Iron
Chapter 1: Increases Samurai attack by 10%
Chapter 2: Increases Archer attack by 10%
Chapter 3: Increases Cavalry Raider attack by 20%
Level 2 (Medieval Age)
Crop Rotation
Chapter 1: Increases Farm limit by 1
Chapter 2: Increases Farm harvest by 5%
Chapter 3: Increases Farm limit by 1
Commerce
Chapter 1: Increases Caravan limit by 1
Chapter 2: Increases income by 5%
Chapter 3: Increases Caravan limit by 1
Ramparts
Chapter 1: Increases Wall limit by 5
Chapter 2: Increases Wall health by 10%
Chapter 3: Increases Wall limit by 5
Chivalry
Chapter 1: Increases Cataphract health by 10%
Chapter 2: Increases Ballista attack by 10%
Chapter 3: Increases Supply Cart healing by 10%
Level 3 (Medieval Age)
Zeal
Chapter 1: Increases Blessing power by 10%
Chapter 2: Increases timed Blessing duration by 50%
Chapter 3: Unlocks a blessing that calls hidden defenders from the forests
Fortification
Chapter 1: Increases Garrison health by 10%
Chapter 2: Increases Garrison defender attack by 10%
Chapter 3: Increases Garrison limit by 1
Battle Tactics
Chapter 1: Increases duration of War Tactics by 20%
Chapter 2: Increases damage and healing of Tactics by 10%
Chapter 3: Increases War Tactics capacity by 1
Ballistics
Chapter 1: Increases Wall Miner health by 10%
Chapter 2: Decreases Ballista troop space by 1
Chapter 3: Decreases Supply Cart troop space by 1
Level 4 (Gunpowder Age)
Hounds
Chapter 1: Increases resources from hunting by 5%
Chapter 2: Increases chance of finding Fur and Leather by 20%
Chapter 3: Increases chance of finding bears and boars
Partisans
Chapter 1: Adds 4 defenders from Town Center
Chapter 2: Increases defender health by 20%
Chapter 3: Increases 4 more more defenders from Town Center
Engineering
Chapter 1: Increases Caltrops limit by 1
Chapter 2: Increases Spike Trap limit by 1
Chapter 3: Increases Ambush Trap limit by 1
Banners
Chapter 1: Decreases Rally cooldown by 5 seconds
Chapter 2: Increases Rally length by 100%
Chapter 3: Increases battle timer length by 15 seconds
Level 5 (Enlightenment Age)
Banking
Chapter 1: Increases Trade Goods storage by 2
Chapter 2: Increases Diamond chance by 20% for 3 or 4 star wins
Chapter 3: Increases Trade Good storage by 2
Citadels
Chapter 1: Increases Ballista Tower health by 10%
Chapter 2: Increases Redoubt health by 10%
Chapter 3: Increases Castle health by 10%
Standing Army
Chapter 1: Increases troop capacity by 2
Chapter 2: Increases troop capacity by 3
Chapter 3: Increases troop capacity by 5
Leadership
Chapter 1: Increases Generals’ health by 10%
Chapter 2: Gives Generals a defender retinue on defense
Chapter 3: Train a second General using oil
Level 6 (Industrial Age)
Drilling
Chapter 1: Increases Oil Well and Refinery health by 20%
Chapter 2: Increases Oil Well production by 10%
Chapter 3: Increases Oil Well limit by 1
Savings
Chapter 1: Vault generates 5% interest after 24 hours
Chapter 2: Increases Vault Food and Gold capacity by 100,000
Chapter 3: Vault can store up to 6,000 oil
Nationalism
Chapter 1: Increases Banker health by 10%
Chapter 2: Increases maximum number of Heavy Tanks spawned by Bunker by 1
Chapter 3: Increases Bunker limit by 1
Heavy Weaponry
Chapter 1: Increases Gatling Gun attack by 10%
Chapter 2: Increases Guerrilla healthy by 10%
Chapter 3: Adds splash damage to Heavy Tank attack