Body Parts

A box is checked on our birth certificate - either male or female. Yet researchers confirm there is a lot of variety in our bodies. Learn about the differences in our bodies that don’t fit within typical male and female boxes.

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Biological sex icon

Hi! I’m here to help you explore the subject of body parts. This is all about biological sex, which, for a long time, was thought to be pretty simple. If you’re born with a penis, you’re a boy, right? It turns out, we are as different on the inside as we are on the outside. In this section, we dig into the science behind biological sex and what it means to more than just male or female. Let’s get started…

The Basics

Explore the many ways in which our bodies can differ.

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Sex redefined

When the box is checked on our birth certificate it represents many complexities. Learn about biological sex and the many unique aspects of our human bodies.

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What it means to be intersex

Get a quick overview of what it means to be intersex.

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Intersex Q&A

Learn about some of the more common intersex variations.

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How common are intersex traits?

Estimates of people who are intersex vary widely. Learn why the numbers vary so significantly.

Intersex controversy and debate

Learn about the controversies surrounding the treatment of children born with an intersex condition, the regulation of intersex athletes, and even the term "intersex" itself.

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Intersex treatment: controversy and debate

The Phall-O-Meter was developed by intersex advocates to draw attention to surgeries performed on babies born with an intersex variation.

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Sorting out terms

Read about variations in terminology and current debates over "intersex" vs. "DSD"

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Intersex athletes

Learn about the debates surrounding intersex athletes including a recent ruling by the Court for Arbitration of Sport.

Real people

Hear from people who are intersex as they talk about their lives and identities.

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"I was born a woman"

Learn about the life and career of Indian runner Dutee Chand, who has challenged efforts to regulate intersex athletes.

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”I was afraid to ask questions"

Hear from four women who are intersex as they reflect on their lives and experiences.

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The Case of Thomas(ine) Hall

Why did a Virginia court in the 1600s order someone to dress as both a man or a woman?

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Forced to leave her country

Tatenda Ngwaru didn't want to leave her home and family in Zimbabwe, but conditions for LGBTQ+ persons left her no choice.

Around the world

Learn about the lives of persons born intersex in other countries.

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Places where intersex is more common

As many as 1 in 90 babies are born intersex in these 2 Dominican villages.

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Living as an intersex person in Australia

Intersex people still face challenges in Australia, even though the country has recently passed anti-discrimination legislation.


Assigned Sex

(Noun) The sex assigned to an infant at birth based on the appearance of genitalia. It’s important to remember that biological sex consists of more than just genitalia, and includes internal reproductive organs as well as sex traits like hormone levels, chromosomes and genes. Learn More


(Noun) A social construct used to classify a person as a man, woman, or some other identity and ascribe qualities of masculinity and femininity to people. Gender characteristics can change over time and vary between cultures. Learn More

Gender dysphoria

(Noun) Clinically significant distress that can occur in persons whose gender identity differs from the sex they were thought to be at birth. Can also describe a desire to change the characteristics that are the source of the distress, such as physical anatomy. Learn More

Gender fluid

(Adj.) Describes a person who identifies their gender as shifting within a spectrum of gender identities and expressions. A person who is gender fluid may always feel like a mix of two (or more) genders, but may feel more one gender some days, and another gender other days. Gender-fluid people may or may not also identify as transgender. Learn More

Gender identity

(Noun) One’s deeply held, core sense of being a man, woman, or some other gender. A gender identity can be a combination of two or more genders (such as gender fluid), and some individuals don't identify with any gender at all--described as being agender. May or may not correspond with the sex or gender assigned at birth. Learn More


(Noun) A term previously used for individuals with atypical sex anatomy that dates to the 14th century. The term hermaphrodite is no longer in use and is considered offensive to intersex individuals due to its longtime association with the view that persons with atypical sex development are inherently problematic. Learn More


(Adj.) An umbrella term for variations in biological sex traits such as genitalia, hormones, reproductive anatomy or chromosomes. Some of these variations are evident at birth while others manifest during puberty or later in life. An intersex person can be of any gender identity and can also be of any sexual orientation and any romantic orientation. Learn More

Legal Transition

(Noun) Refers to the process through which a transgender person changes names and/or sex/gender categories on legal documents. These documents can include an updated driver’s license, social security card, and birth certificate. Other changes might involve changing government, work, school, bank and other institutional records. Learn More


(Adj.) An identity that does not conform to traditional two-sided categories of sex, gender, and/or sexual orientation, such as male-female, man-woman, and gay-straight. Learn More

Sex / Sex assigned at birth / Biological sex

(Noun) A person's sex (male, female, or intersex) is often determined based on the appearance of the genitalia, either in ultrasound or at birth. In reality, biological sex is more complicated, referring to a combination of anatomical, physiological, genetic, and physical attributes. These include genitalia, gonads, hormone levels, hormone receptors, chromosomes, genes, and secondary sex characteristics. The phrase "sex assigned at birth" is used by some to emphasize that genitalia alone are not always a sufficient indication of a person's sex, as well as the fact that a person's gender identity is not always aligned with the sex characteristics observed at birth. Learn More

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Citations & Sources

Ainsworth, C. (2015). Sex redefined: The idea of two sexes is simplistic. Biologists now think there is a wider spectrum than that. Nature, 518, 288-291.!/menu/main/topColumns/topLeftColumn/pdf/518288a.pdf

APA Task Force on Gender Identity, Gender Variance, and Intersex Conditions (2006). Answers to your questions about individuals with intersex conditions [Pamphlet]. American Psychological Association.

Block, M. (2016, August 16). The sensitive question of intersex athletes. NPR.

Coleman, D. (2018, April 30). Sex, sport, and why track and field's new rules on intersex athletes are essential. New York Times.

Dreger, A. (2018, April 27). Track's absurd new rules for women. New York Times.

DSD research. (n.d.). Accord Alliance.

Feder, E. & Karkazis, K. (2008). What’s in a name? The controversy over “Disorders of Sex Development”. The Hastings Center Report, 38(5), 33-36.

Fogle, A. (2016, October 21). Falling in between: Inside the lives of intersex women. Good Housekeeping.

Gender Issues in Agriculture AGEX3003. (n.d.) Growing up intersex part 1 [Video]. YouTube.

Ghcorayshi, A. (2017, July 26). A landmark lawsuit about an intersex baby’s genital surgery just settled for $440,000. BuzzFeedNews.

Greenfield, C. (2014, July 8). Should we ‘fix’ intersex children? Atlantic.

Hartney, E. (2018, February 7). What does it mean to be intersex? Verywell Mind.

Padawer, R. (2016, June 28). The humiliating practice of sex-testing female athletes. New York Times Magazine.

Reardon, Sara. (2016). The spectrum of sex development: Eric Vilain and the intersex controversy. Nature, 533(7602), 160-163.

Ritchie, R., Reynard, J., & Lewis, T. (2008). Intersex and the Olympic Games. Journal of the Royal Society of Medicine, 101(8), 395-399.

Sleath, E. (2014, December 2). I am intersex: Shon Klose’s story. ABC.

Topol, S. (2017, August). Sons and daughters: The village where girls turn into boys. Harper’s Weekly.

Viewpoints on DSD care. (n.d.). Accord Alliance.

World Athletics. (2018, April 26). IAAF introduces new eligibility regulations for female classification [Press release].

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