An optically variable device, the device comprising: a control element or layer; one or more responsive optical element(s); optionally a spacer layer between the control element or layer and the responsive optical element(s); the control element or layer and the responsive optical element(s) moveable in the device relative to one another upon application of an external influence upon the device, to change the distance of separation of the control element or layer from the responsive optical element(s), the control element or layer and/or the responsive optical element(s), comprising a material with a surface plasmon resonance that is influenced by proximity of the material to the other of the control element / layer or the responsive optical element(s); the relative movement and/or a resulting change of surface plasmon resonance of the material causing a detectable or perceivable change in the optical properties of the device; wherein the responsive optical elements form, or are present in, a responsive optical layer, and wherein the responsive optical layer and/or the spacer layer, if present, comprises a deformable material, changeable between a relaxed state, and a compressed state when the external influence is exerted upon the device, resulting in a change in the distance of the responsive optical element(s) from the control layer, and thus a change in the optical properties of the responsive optical layer; and wherein upon removal or reduction of the external influence, the responsive optical layer and/or the deformable spacer layer if present of said device relaxes from said compressed state to said relaxed state, optionally in a time of from 0.001 to 120 seconds, characterised in that the external influence is in the form of mechanical pressure. a control element or layer; one or more responsive optical element(s); optionally a spacer layer between the control element or layer and the responsive optical element(s); the control element or layer and the responsive optical element(s) moveable in the device relative to one another upon application of an external influence upon the device, to change the distance of separation of the control element or layer from the responsive optical element(s), the control element or layer and/or the responsive optical element(s), comprising a material with a surface plasmon resonance that is influenced by proximity of the material to the other of the control element / layer or the responsive optical element(s); the relative movement and/or a resulting change of surface plasmon resonance of the material causing a detectable or perceivable change in the optical properties of the device; wherein the responsive optical elements form, or are present in, a responsive optical layer, and wherein the responsive optical layer and/or the spacer layer, if present, comprises a deformable material, changeable between a relaxed state, and a compressed state when the external influence is exerted upon the device, resulting in a change in the distance of the responsive optical element(s) from the control layer, and thus a change in the optical properties of the responsive optical layer; and wherein upon removal or reduction of the external influence, the responsive optical layer and/or the deformable spacer layer if present of said device relaxes from said compressed state to said relaxed state, optionally in a time of from 0.001 to 120 seconds, characterised in that the external influence is in the form of mechanical pressure.