The word Tantra itself is derived from the verbal root tan, meaning to "weave". Many things are interwoven on the Tantric path, including the lives of men and women. The Buddha couples of Tantric iconography celebrate this deep harmony of the sexes. The purpose of this dynamic was the creation of partnerships devoted to the realization of the ultimate truth. For instance, the man cultivates pure vision by seeing the woman as a deity, her sexual organ as the throne of enlightenment, and her sexual fluid as divine nectar. Thus according to the Brhadaranyaka Upanisad, sexual union also constitutes a fire sacrifice, as performed by the creator god Prajapati upon creating woman:

Having created her, he worshipped her sexual organ;
Therefore a woman's vulva should be worshipped.
He stretched forth from himself a stone for pressing nectar
[i.e., causing a woman's sexual fluid to flow]
And impregnated her with that.
Her lap is the sacrificial altar;
Her hair, the sacrificial grass;
Her skin the soma press;
The labia of her vulva, the fire in the middle.
. . . . . . . . .
Many mortals...go forth from this world...without merit,
Namely, those who practice sexual union without knowing this.

Brhadaranyaka Upanisad 6.4.1-4

Often the mother is shown in a posture with both legs around the father's waist. In this remarkable and richly symbolic manifestation, both the male and the female are emanations of the Buddha. They appear simultaneously united and independent, like the complex relationship of sameness and difference between wisdom (female) and compassion (male) in the enlightened state. Ponderous, energetic forms confront the viewer in this stunning portrayal. Shamvara (supreme bliss) embraces the massive sky blue body of his consort Vajravarahi, holding in his hands various implements symbolic of his triumph over ignorance and evil. She gazes rapturously and intently at her consort with her head thrown back, heightening their electrifying aura. Two of her arms tightly clutch Shamvara's neck. His first two arms embrace his consort, and holding a Vajra and a bell make the diamond HUM- sound gesture with the crossed wrists, behind her back. This gesture celebrates the inseparable union of method and wisdom.

The father-mother union image is not an example of erotic art, but is a manifestation of the Buddha's highest spiritual essence. More than metaphorical, to the devout Tibetan this image is concrete evidence of the existence of great spiritual attainment. The female (mother) represents transcendent wisdom: the direct awareness of reality as the Buddha experienced it and taught it. The male (father), represents compassion for all beings, which is the natural expression of such wisdom. Their union, although exquisitely blissful, is ultimately undertaken out of compassion for the world. This sacred communion of the male and female Buddha generates waves of bliss and harmony that turn the world into a Mandala (container of essence) and showers forth a rain of nectar that satisfies the spiritual hunger in the hearts of living beings everywhere. Modern depth psychology has recognized such images to represent the deepest archetypes of the unconscious, integrating the powerful instinctual energies of life into a consciously sublimated and exalted state.
The union of a lotus and vajra, or diamond scepter. Clearly, "lotus" and vajra are metaphors, not literal terms. One is not meant to bring together a flower and a scepter, but something denoted by these terms. Depending upon the level of interpretation, uniting the lotus and the vajra can mean uniting wisdom and compassion, or bliss and emptiness, within the practitioner's psyche, or bringing together the female and male organs in physical union.