Estrogen are very important chemical compounds very essential for our body functions. The cholesterol, what we eat through food, gets converted by the action of various enzymes. Scientists have synthesized estrogenic molecules in the laboratory and used them for oral contraceptives and other therapeutic purposes. Environmental estrogenic molecules (xenestrogen) played havocs in human life. Plants also make estrogenic substances (phytoestrogen); they are very useful for mankind. All steroid hormones, including estrogen are synthesized from cholesterol through a common precursor steroid, pregnenolone which is formed by the enzymatic cleavage of a 6-carbon side-chain of the 27-carbon cholesterol molecule. Cholesterol is a starting substance of group of estrogenic compounds [1]. On the other hand, synthetic estrogen are compounds obtained by chemical synthesis that possess estrogenic activity [2]. In addition to these estrogenic compounds there are some estrogenic action mimicking compounds known as xenestrogen and phytoestrogen (Figure 1).