Well, we read a lot about how in vitro manipulation of oocytes can induce stress and therefore reduce their potential or as people call it "quality". I've been looking into the studies mostly, they focus on the oxidative stress and reactive oxygen species relation with calcium regulation. Other studies investigated the heating as a stress factor. Well, how they established that this oocyte is healthy and this one is stressed? On what basis? What kind of methods they used? Are the polscope data useful?