There are several methods of producing a new transponder (chip) car key. It is far easier and cheaper to copy an existing car key. If you’ve lost all the keys it is often possible to program a new key diagnostically. If that can’t be done it may be necessary to remove the immobiliser (aka ECU, EWS) and write information directly to the chip on the board. This may require stripping off your dashboard or clocks to get to it. It is more expensive a procedure than diagnostic programming
In this picture we are EEPROM programming a new key into a Fiat Punto immobiliser.