It's begun to edge into the mainstream that gender isn't everything we thought it was. RTÉ journalist Jonathan Clynch revealed this weekend how he identifies as gender fluid, and his story opened up an important conversation about gender identity.
Over the past few months, celebrities Miley Cyrus and Ruby Rose have also spoken publicly about identifying as gender fluid.
While you might have put Miley's transition from the very girlie Hannah Montana to her now androgynous style down to a simple sartorial choice, the child star has announced she doesn't want to be boxed into one gender identity.
"I didn't want to be a boy … I kind of wanted to be nothing," she said.
"I don't relate to what people would say defines a girl or a boy, and I think that's what I had to understand: Being a girl isn't what I hate, it's the box that I get put into."
Meanwhile, Ruby Rose, the actress from cult hit 'Orange Is the New Black', shared a rare insight into being gender fluid in her short film 'Break Free', where she transitioned from an ultra-feminine version of herself with luscious blonde hair to a masculine version wearing a suit.
"The only reason it was a surprise was because gender fluidity doesn't get talked about enough," she said.
"Once the film went viral, the floodgates opened. To me, that said that this was something much bigger than I thought it was."
Exact statistics about gender fluidity don't exist, but experts estimate that somewhere between 1pc and 8pc of the population are "gender diverse".
This includes being gender-fluid, gender-queer (a person who identifies as neither sex) and transsexual (a person who identifies as the opposite sex).
However, the notion that there are only two possible genders and that those genders are rigid and fixed is an organising principle of life in every society. It affects absolutely everything, from how we dress to who we can marry and what work we get - and how much we will be paid for that work.
This is why gender fluidity can be a bit unsettling, because discussion on issues like intersexuality challenges all that. It gives the lie to the gender binary, exposing it as not just flawed, but scientifically inaccurate. As part of a non-binary identity, gender may be a more fluid concept, so the idea of a 'fixed' gender just isn't appropriate.
Because of this fluidity, someone's identity and how they see themselves in the world might change over time. And that's exactly how this affects lots of people.
In 2013 Germany introduced legislation to allow parents not to record the gender of their newborn. German law provided the right to 'leave the box blank' only to those born intersex - but gender identity is about more than biology.
According to a 2012 Scottish trans mental health study, about a quarter of transsexual and transgender people do not identify as male or female, and prefer to present as nonbinary, gender-fluid or agendered. Still Germany's new law was a small step towards equal rights and recognition for intersex, transsexual and transgender people in Europe.
Stories like that of Jonathan Clynch are going to mean nothing to a lot of people, but for the few it does affect, it means the world.
Among the findings of a survey by the Transgender Equality Network Ireland, we discovered 78pc of trans respondents had thought about ending their life, with 63pc of respondents saying they thought about attempting suicide in the last year and 40pc of respondents saying they had attempted suicide in their life.
Right now, children - including intersex and transgender kids - grow up believing you have to be a girl or a boy and that there are no other options.
We've only recently begun to recognise gender diversity and understand that what a doctor sees between a baby's legs doesn't always determine a person's true gender. It can't predict how that person's brain will continue to develop.
Perhaps the generation born today will grow up with different assumptions; that gender might not be the most important part of your identity, even if that's still an uncomfortable idea for many of us.
It's always unnerving to have conventions challenged, but isn't that pretty much what progress is all about? I'm thinking of what it took for us to realise the earth was round or - as we're also experiencing now - that marriage rights should be equal for everybody.