We have long known men's shirts have their buttons on the right - while women's blouses button on the left.
But it's safe to say no one has given much thought to why - until now.
A debate has broken out over the reason for the difference, after someone posted the seemingly straightforward question on an internet forum.
Writing on the website Quora, which allows users to post questions for those with expertise on the matter to answer, commenters came up with countless theories ranging from the archaic to the ridiculous. One user, Will Wister, claimed the side on which buttons are sewn is historically related to how the different genders got dressed.
He said: "Women were dressed by servants who tended to be right-handed, while men tended to dress themselves."
However, others argued that men were also dressed by servants in the 17th and 18th centuries.
Mr Wister also put forward another theory, writing: "Portraits of Napoleon often depict him with his right hand tucked into his coat, which is only possible because of left-to-right buttoning.
"Napoleon ordered that all women's shirts be buttoned on the opposite side because women used to stick their hands in their shirts to mock him.
"With the buttons on the opposite side, women could no longer mock him."
But according to user Gwen Sawchuk, the answer is in fact related to breastfeeding for women - and self-defence for men. She said: "Women usually hold a baby on their left arm, so their right hand is free to unbutton a blouse for suckling. Men defend themselves with their right hand (sword, or fist) and thus their left hand is available to adjust their clothing."
Others had more bizarre theories. Hanna Svenonius claimed the buttons were designed to stop parishioners getting too excited in church. "Men and women traditionally sat on different sides of the centre aisle, so buttoning the shirts differently made sure nobody could sneak a peek at some naked chest of the opposite sex," she wrote.