Science has a pretty decent menagerie of glowing animals, what with all the pigs and cats and rabbits and mice. All those glowing animals, though, have one thing in common: they ' ve been genetically modified with jellyfish DNA. A recent experiment conducted by researchers at the University of Toronto has resulted in glowing mice with a difference: they've been injected with nanoparticles that glow under UV light. Why? With the rising use of nanoparticles, precisely how they might affect our health has become a concern. "The increasing use of nanomaterials raises concerns about the long-term effects of chronic nanoparticle exposure on human health," the researchers explained. "However, nanoparticle exposure is difficult to evaluate non-invasively using current measurement techniques. Here we show that the skin is an important site of nanoparticle accumulation following systemic administration." The experiment, which allowed researchers to determine for the first time nanoparticle accumulation in a living body, saw the mice injected with two different types of nanoparticles: gold nanoparticles, and light-sensitive nanoparticles called quantum dots. They found that the mice injected with high doses of gold particles turned blue, while those injected with quantum dots lit up in fluorescent patterns when under UV light. Moreover, a skin biopsy demonstrated that the accumulation of nanoparticles in the skin corresponded with the accumulation in the liver and spleen. This means that a simple skin biopsy may be enough to diagnose nanoparticle exposure and accumulation, and predict how nanoparticles behave in the human body. The full paper, "Nanoparticle exposure in animals can be visualized in the skin and analysed via skin biopsy", was published in the journal Nature.