The psychoanalytical concept of penis envy is unrelated to the "small penis syndrome" which is the anxiety of thinking one's penis is too small[3] (though Otto Fenichel did explore the possibility of a boy's envy for the adult [paternal] penis).[4]
In Freud's psychosexual development theory, the phallic stage (approximately between the ages of 3.5 and 6) is the first period of development in which the libidinal focus is primarily on the genital area. Prior to this stage, the libido (broadly defined by Freud as the primary motivating energy force within the mind) focuses on other physiological areas. For instance, in the oral stage, in the first 12 to 18 months of life, libidinal needs concentrate on the desire to eat, sleep, suck and bite. The theory suggests that the penis becomes the organ of principal interest to both sexes in the phallic stage. This becomes the catalyst for a series of pivotal events in psychosexual development. These events, known as the Oedipus complex for boys, and the Electra complex for girls, result in significantly different outcomes for each gender because of differences in anatomy.
For girls:
Soon after the libidinal shift to the penis, the child develops her first sexual impulses towards her mother.
The girl realizes that she is not physically equipped to have a heterosexual relationship with her mother, since she does not have a penis.
She desires a penis, and the power that it represents. This is described as penis