Cancer cells take up spaser nanoparticles. Breast cancer cells were incubated with nanoparticles with “surface plasmon amplification by stimulated emission of radiation” (spasers) composed of a gold sphere in the core and a silica shell containing the fluorescent dye uranine. These cancer cells took up the particles. From Galanzha et al. Spaser as a biological probe. Nat. Commun. 8, 15528 doi: 10.1038/ncomms15528 (2017).