We report the first application of single-wall carbon nanotubes (SWCNT) as potent therapeutic nanobomb agents for killing breast cancer cells. We show here that by adsorbing water molecules in SWCNT sheets or loosely adsorbed on top of cells, potent nanobombs were created that heated the water molecules inside them to more than 100°C upon exposure to laser light of 800 nm at light intensities of ~50-200 mW/cm2. Conversion of optical into thermal energy, and the subsequent confinement of thermal energy in nanotubes caused the water molecules to evaporate and develop extreme pressures in nanotubes causing them to explode in solutions. Co-localized nanobombs killed human BT474 breast cancer cells in physiological phosphate buffered saline solution (PBS). Cells that were treated with nano-bombs exploded into fragments, while the surrounding cells not treated with nano-bombs were viable. Nanotube based nano-bombs can outperform most nanotechnological approaches in killing cancer cells.