Manstruation

Menstruation is a natural thing; it happens in some bodies, and does not in others. Gender holds no bearing over whose bodies do and do not menstruate. In fact, the only field that really has any influence in the way of menstruation is biology (human anatomy and physiology, to be specific). Gender is socially constructed, it has no biological basis whatsoever. Why then, do we feel the need to associate menstruation with femaleness? Not all womxn/girls (cis and trans alike) are able to menstruate, and not all people who menstruate are female. Furthermore, from that same association, stigma against a natural bodily cycle has developed. Because femaleness is seen as "lesser", the association of menstrual cycles with femaleness has tainted the public view so that now people are shamed for basic (albeit, necessary for sustaining the human race) bodily functions simply because they have been deemed "feminine".  As a result, "periods" are often seen as "gross"/unsanitary, "inappropriate", and taboo. Access to necessary supplies and resources (OB/GYN services, pads and tampons, birth control, et cetera) is therefore limited because it is treated as a burden (sometimes referred to as a "preexisting condition") and not as a natural part of life, so the related goods and services are priced as commodities (and sometimes even luxuries) rather than as necessities (and that is going off of the assumption that our healthcare system here is a normal standard, when it is actually a capitalist, for-profit scheme itself, offsetting the difference even more).
This also greatly affects the education surrounding menstruation, which many people are lacking. Though education has improved since its creation, one stark cultural example of this is in the story of "Carrie" (initially, the 1974 novel written by Stephen King, later reproduced three times into movie adaptations), a young girl in high school whose education is so sorely lacking that, upon her first menstrual bleed, she believed she was dying. This could easily have been prevented had Carrie had access to proper education about reproductive bodily functions, but due to the stigma, she had to suffer because no one felt it important to talk to her.
Unfortunately, this stigma, shaming, and feminization of menstruation also largely contribute to bodily dysphoria and/or misgendering for many people. For some, they are seen as not womxn because they cannot menstruate (be they cis or trans). For others, they may have been C/AFAB (coercively/ assigned female at birth) non-womxn who do menstruate, but are either denied their genders due to menstruation or else feel like their gender is not valid (or at least seen that way) due to their bodies' participation in a menstrual cycle. Many transmasculine people will refer to it as "manstruation" because it is a tongue-in-cheek way of still addressing the issue at hand, while helping them feel slightly less dysphoric or otherwise denied their identities. Other terms that have been adopted in such a way include (but are not limited to): brovaries, duderus, breasticles, and chesticles. The common theme here is masculinizing menstruation. We should not have to masculinize something to make it more palatable or acceptable, especially not something that is (when we're being honest about it, outside of sociopolitical context) a non-gendered, fairly regular bodily function. I say this as someone who regularly experiences this dysphoria and often makes use of the term "manstruation": it is ridiculous. Men's obsession with making anything and everything associated with womxn (and girls) seen as "less acceptable" or all around "negative" has got to stop; this is ridiculous and harmful, and we need to make a change. People should not have to tiptoe around or politicize basic bodily functions; there's just no reason for it.