In anatomy, heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. Heterochromia is a result of the relative excess or lack of melanin (a pigment). It may be inherited, or caused by genetic mosaicism, disease, or injury.

Heterochromia of the eye (heterochromia iridis or heterochromia iridum; the common wrong form "heterochromia iridium" is not correct Latin) is of two kinds. In complete heterochromia, one iris is a different color from the other. In partial heterochromia or sectoral heterochromia, part of one iris is a different color from its remainder.

Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). In humans, usually, an excess of melanin indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia.

Heterochromia is classified primarily by onset: as either genetic or acquired. Although a distinction is frequently made between heterochromia that affects an eye completely or only partially (sectoral heterochromia), it is often classified as either genetic (due to mosaicism or congenital) or acquired, with mention as to whether the affected iris or portion of the iris is darker or lighter.

Alice Sophia Eve (born 6 February 1982) is an English actress. She is known her roles films such as She's Out of My League, Sex and the City 2, Men in Black 3. She will also star in the upcoming The Decoy Bride.

Eve was born in London, England, the daughter of actors Trevor Eve and Sharon Maughan. She has two younger brothers, Jack and George. Eve is of English, Welsh and Irish descent. She attended Bedales School and then took her A-Levels at Westminster School in London. During her gap year, she studied at the Beverly Hills Playhouse and then read English at St Catherine's College, Oxford. While at Oxford, she appeared in student productions of An Ideal Husband, Animal Crackers (which toured to the Edinburgh Fringe Festival), Scenes from an Execution and The Colour of Justice.^{[citation needed]}

Eve has starred in television dramas including the BBC's The Rotters' Club, Poirot and Hawking as well as the film Stage Beauty (2004).

Eve played significant roles in two 2006 films: Starter for 10 and Big Nothing (in which she and co-star Simon Pegg used American accents). She spent the early part of 2006 in India working on a drama mini-series Losing Gemma about backpackers.