Embryonic development is a complex process that is defined by many factors. But in general, we can say that it is affected by 2 important sources of change: genes and environment. Genes hold the necessary information that will dictate how the embryo will develop and the characteristics it will have. However, the environment will define which genes will be expressed and carry out their function and which genes will be "dormant or silenced" and have no effect on the development of the embryo. Therefore, both are equally important, since on the one hand, if the genes did not exist, the embryo would not have the necessary information to develop. On the other hand, if the cells did not respond to the inhibitory stimuli of the environment, for example, they would multiply unceasingly leading to the malformation or death of the embryo.