Fuel injector of an internal combustion engine and internal combustion engine

A fuel injector of an internal combustion engine, configured to supply fuel to a combustion chamber of a cylinder of the internal combustion engine, comprising:

• a first nozzle needle moveably guided in a first needle guide, which interacts with first fuel injection orifices such that depending on a first nozzle needle position, either opens or blocks a fuel flow of a first fuel through the first fuel injection orifices;
• a second nozzle needle moveably guided in a second needle guide, which interacts with second fuel injection orifices such that depending on a second nozzle needle position, either opens or blocks a fuel flow of a second fuel through the second fuel injection orifices;
• a fuel storage space;
• and
• a piston moveably guided in the fuel storage space, wherein the piston divides the fuel storage space depending on its position in the fuel storage space, into a first fuel storage subspace for the first fuel and into a second fuel storage subspace for the second fuel.