Apparatus and methods are described for killing cancer cells (44) of a subject, the subject having cancer cells and healthy cells. The apparatus includes a plurality of first molecules (40) configured to be coupled to the cancer cells to a greater extent than to the healthy cells, in response to being administered to the subject. A plurality of clusters (42) of phase-change molecules are provided, each of the clusters coupled to a respective one of the first molecules. An energy transmission unit (50) kills cancer cells coupled to the first molecules by heating the cancer cells, by transmitting energy toward the clusters that selectively heats the clusters. Other embodiments are also described.
