Fluorescent crystal formation marks mercuric ion. Selective
precipitation of the ligand developed by Janda, Dickerson, and La Clair in the presence of fluorescent dye generate crystals with nanometer to micrometer dimensions. Image by J. La Clair.

Combining a ligand molecule (yellow) with mercuric ion (silver ball) generates a complex that precipitates rapidly out of solution. The clusters of microcrystalline precipitates falling out of solution form a mat (silver surface), which can be imaged using a variety of CCD-based detection systems. Artwork by J. La Clair.