Figure 1. Sperm fusion with the egg induces repetitive Ca²⁺ oscillations in the mammalian zygote.

A. Eggs loaded with a Ca²⁺ fluorescent dye (Fluo-3) were monitored for changes in fluorescence after addition of sperm. Unfertilized eggs had low fluorescence (blue signal) whereas fertilized zygotes exhibited transient peaks of fluorescence (red signal). B. Quantification of the fluorescence changes recorded in a fertilized zygote.