A team of researchers has created a way to control the length of time light from a luminescent nanocrystal lingers, adding a new dimension of time to color and brightness in optical detection technology. This exponentially boosts the number of different combinations that can be created and used as unique tags for biomedical screens. In addition, light emitted by the new nanocrystals far outlasts that which occurs naturally in biological systems. That difference in timing distinctly separates the signal from background noise.