A method and apparatus is provided for non-invasively mixing ingredients in closed containers. Mixing is performed by inducing waves in the liquid to be mixed. This is achieved by rocking the container in precise phase so as to produce resonance. With the waves moving back and forth in resonance, it is possible to mix with very low energy requirements compared to prior art. Mixing ingredients with resonant waves in a closed container eliminates the need for an invasive mixer and has obvious advantages in minimizing contamination. This makes the device ideal for biological processing that typically require sterile operation.