What is emasculation? Why and when is it done?

Emasculation is the process of removal of male reproductive part (stamens) from the flower, usually a bisexual flower.

Emasculation is done so that the flower becomes completely a female flower and there is no chance of self pollination or pollination by undesirable pollen. Emasculation is an important technique in hybridisation. It is done before the flowers attain maturity.