What is emasculation? Why and when is it done?

(N/A) Emasculation is the process of removing the anthers from a bisexual flower.
It is performed to prevent self-pollination,ensuring that the plant is used only for cross-pollination in artificial hybridization programs.
It is done before the dehiscence of the anthers to ensure that the pollen grains do not mature and release,thus preventing self-fertilization.