Apparatus for use with a subject suffering from cancer, a body of the subject containing cancerous cells and non-cancerous cells, and for use with a heating device configured to heat at least a portion of the subject's body, the apparatus comprising: a nanoparticle comprising: an inner core; an outer layer disposed around the inner core, the outer layer comprising: a plurality of nano-spheres of at least one metal; and a plurality of molecules of a substance that binds preferentially with cancerous cells relative to non-cancerous cells, the nanoparticle having a volume of at least 65,000 nm 3, characterized in that: the inner core comprises a phase-change material that is configured to absorb latent heat of fusion by undergoing a phase change selected from the group consisting of: solid to liquid, and gel to liquid, the phase-change occurring at a phase-change temperature of between 42°C and 80°C; the outer layer is not a continuous layer, with separations between each of the nano-spheres and the nano-spheres adjacent thereto allowing the nano-spheres to move with respect to each other; and the nanoparticle, by virtue of each of the nano-spheres being separated from others of the nano-spheres of the outer layer, being elongatable into an ellipsoid, such that when the nanoparticle is maximally elongated: each of the semi-axes defined by the ellipsoid is greater than 5 nm, and at least two of the semi axes of the ellipsoid are less than 30 nm. a nanoparticle comprising: an inner core; an outer layer disposed around the inner core, the outer layer comprising: a plurality of nano-spheres of at least one metal; and a plurality of molecules of a substance that binds preferentially with cancerous cells relative to non-cancerous cells, the nanoparticle having a volume of at least 65,000 nm 3, an inner core; an outer layer disposed around the inner core, the outer layer comprising: a plurality of nano-spheres of at least one metal; and a plurality of molecules of a substance that binds preferentially with cancerous cells relative to non-cancerous cells, the nanoparticle having a volume of at least 65,000 nm 3, a plurality of nano-spheres of at least one metal; and a plurality of molecules of a substance that binds preferentially with cancerous cells relative to non-cancerous cells, the nanoparticle having a volume of at least 65,000 nm 3, characterized in that: the inner core comprises a phase-change material that is configured to absorb latent heat of fusion by undergoing a phase change selected from the group consisting of: solid to liquid, and gel to liquid, the phase-change occurring at a phase-change temperature of between 42°C and 80°C; the outer layer is not a continuous layer, with separations between each of the nano-spheres and the nano-spheres adjacent thereto allowing the nano-spheres to move with respect to each other; and the nanoparticle, by virtue of each of the nano-spheres being separated from others of the nano-spheres of the outer layer, being elongatable into an ellipsoid, such that when the nanoparticle is maximally elongated: each of the semi-axes defined by the ellipsoid is greater than 5 nm, and at least two of the semi axes of the ellipsoid are less than 30 nm. the inner core comprises a phase-change material that is configured to absorb latent heat of fusion by undergoing a phase change selected from the group consisting of: solid to liquid, and gel to liquid, the phase-change occurring at a phase-change temperature of between 42°C and 80°C; the outer layer is not a continuous layer, with separations between each of the nano-spheres and the nano-spheres adjacent thereto allowing the nano-spheres to move with respect to each other; and the nanoparticle, by virtue of each of the nano-spheres being separated from others of the nano-spheres of the outer layer, being elongatable into an ellipsoid, such that when the nanoparticle is maximally elongated: each of the semi-axes defined by the ellipsoid is greater than 5 nm, and at least two of the semi axes of the ellipsoid are less than 30 nm. each of the semi-axes defined by the ellipsoid is greater than 5 nm, and at least two of the semi axes of the ellipsoid are less than 30 nm.