In the sci-fi novel "The Diamond Age" by Neal Stephenson, body art has evolved into "constantly shifting mediatronic tattoos" - in-skin displays powered by nanotech robopigments. In the 25 years since the novel was published, nanotechnology has had time to catch up, and the sci-fi vision of dynamic tattoos is starting to become a reality.

The first examples of color-changing nanotech tattoos have been developed over the past few years, and they're not just for body art. They have a biomedical purpose. Imagine a tattoo that alerts you to a health problem signaled by a change in your biochemistry, or to radiation exposure that could be dangerous to your health.

You can't walk into a doctor's office and get a dynamic tattoo yet, but they are on the way. Early proof-of-concept studies provide convincing evidence that tattoos can be engineered, not only to change color, but to sense and convey biomedical information, including the onset of cancer.