English: Movies show the dynamics of cytoplasmic movement in developing embryos. To facilitate visualization of the movement at the surface of the embryo, black particle tracers were added to the images by using the image analysis software. (Top) In embryos developed in a microfluidic device at uniform 23°C, minimal cytoplasmic movement is observed. (Bottom) In embryos developed in a microfluidic device exposed to a temperature step with anterior (left) at 20°C and posterior (right) at 27°C, dramatic cytoplasmic movement is observed, with net movement from the warm to the cool half of the embryo.