Spectral variants of the green fluorescent protein (GFP) are quite useful for double or triple labeling experiments or when targeting fluorescence expression with a particular laser system. The confocal image presented above is a three-dimensional volume render made from 5-micrometer serial optical sections of a zebrafish embryo labeled with a red fluorescent protein (dsRED). The image was provided by Yasuhiro Kamei and Shunsuke Yuba of the Institute for Molecular and Cellular Biology at Osaka University, in Japan.