An electrically operated, single cell memory element comprising: a volume of memory material defining a single-cell memory element, the memory material comprising a heterogeneous mixture of a phase-change material and a dielectric material; and means for delivering an electrical signal to at least a portion of the volume of memory material. An electrically operated, single-cell memory element comprising: a volume of memory material defining the single-cell memory element, the memory material comprising a phase-change material and a dielectric material where the phase-change material has a plurality of detectable resistivity values and can be set directly to one of the resistivity values without the need to be set to a specific starting or erased resistivity value, regardless of the previous resistivity value of the material, in response to an electrical signal; and means for delivering the electrical signal to at least a portion of the volume of memory material.