A liquid handling system that is configured to receive an interchangeable pipetting head that is selected from a plurality of interchangeable pipetting heads for automated liquid handling flexibility and scalability. The system includes a housing and at least one pipetting head disposed within that housing for aspirating and dispensing a liquid. A locking mechanism interchangeably receives the at least one pipetting head and includes an adaptor plate and a support block. The adaptor plate is operably coupled to the housing and the support block is operably coupled to the at least one pipetting head. The support block is then, in turn, is configured to be operably coupled to the adaptor plate.