This week we we zoom in on the subject of nano-particles to examine how tiny objects, smaller than the wavelength of light, can be making such large waves in the fields of health, optics, and electronics. Plus news of purple tomatoes on their way to your dinner plates, the medical treatment that could mean the end of peanut allergies, the acid dip that reverts cells to their stem state, and what's in the air in Beijing? Like this podcast? Please help us by supporting the Naked Scientists)