Condensed matter systems that are both low dimensional and strongly interacting often exhibit unusual electronic properties. Strongly correlated electrons with greatly enhanced effective mass are present in heavy fermion compounds, whose electronic structure is essentially three-dimensional. We experimentally realize a two-dimensional heavy fermion system, adjusting the dimensionality in a controllable fashion. Artificial superlattices of antiferromagnetic heavy fermion compound CeIn 3 and

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... ntional metal LaIn 3 are grown epitaxially. By reducing the CeIn 3 -layer thickness, the magnetic order is suppressed and the effective electron mass is further enhanced. Heavy fermions confined to two dimensions display striking deviations from the standard Fermi liquid low-temperature electronic properties, associated with the dimensional tuning of quantum criticality.