You must research and upgrade Tech in order to gain access to new types of Buildings and Units. You can view all Tech from the Tech Center or via the Tech tab of your Action Panel. Upgrading the Tech Center allows you to research and upgrade Tech faster.
You will need Rations, Fuel, and Munitions to research Tech. Some Tech also requires Intel Files. Alternatively, you may use Diamonds to complete Tech Research and Upgrade processes.
The cost of upgrading a given Tech will become progressively more expensive with each Level, and the time required for signing will become longer.
While there is no specific order in which Tech must be researched, some Tech requires you to research or upgrade other Tech, or alternatively upgrade certain Buildings first.
Unless you open an Extra Research Slot, you may work on one Tech at a time.