Egg activation is the critical step in which the developmentally arrested oocytes shifts to begin embryogenesis. This process is characterized by a rise of intracellular free calcium levels, beginning at one region of the oocyte and sweeping across the whole egg. This Ca2+ rise triggers downstream events including meiosis resumption and changes in the transcriptome and proteome. Although in vertebrates and marine invertebrates fertilization triggers the Ca2+ rise, in Drosophila it is triggered prior to fertilization in the form of a wave that starts at pole of oocytes. This calcium wave is induced by physical forces that occur during ovulation. Genetic studies and inhibitor tests suggest that these forces activate mechanosensitive ion channels in the oocyte that then let in Ca2+ from extracellular environment. Currently we are using chemical, physical, and genetic means to identify the ion channels that introduce Ca2+ into the oocyte, and to determine how and where they act and are regulated.