Mitotic divisions in early Drosophila embryos. The spindles were labeled with an anti–a-tubulin primary antibody and probed with a secondary antibody labeled with Lissamine rhodamine B sulfonyl chloride (Cat. No. L20, L1908). After a brief RNase treatment to reduce background fluorescence, the chromosomes were counterstained with SYTOX® Green nucleic acid stain (Cat. No. S7020). The image was contributed by Tulle Hazelrigg and Amy MacQueen, Columbia University.