The modern monarchy is progressive in so many ways. From Prince Harry and Meghan Markle's thoroughly modern (with still a strong nod to tradition) wedding, to Princess Charlotte becoming the first female royal in history to not be bumped down the line to the throne with the arrival of her younger male brother Prince Louis.
But some traditions are here to stay, and perhaps the most intriguing of them all is the curtsy.
While we greet family members with a hug or high five (think junior members), royal females from Great Britain or Europe must curtsy to anyone above them in the royal social order.
The gesture - a deep and elaborate dip known as the "court curtsy" - is the ultimate mark of respect.
"The royal curtsy is one foot behind the other and the deep and the longer you stay down shows more respect," Australian School of Etiquette, Zarife Hardy tells Now To Love.
Interestingly, after Catherine, Duchess of Cambridge, married Prince William in 2011 The Queen reportedly updated the Order of Precedence document so that even though Duchess Catherine is now higher in the pecking order than "blood princesses" such as Princess Royal, Princess Alexandra, and the daughters of the Duke of York, Princesses Beatrice and Eugenie, she must curtsy to them.
This rule does not apply, however, if the Duchess of Cambridge is joined by Prince William.
We take a look back at some of the best royal curtsies we've seen over the years, from From Princess Diana to Catherine, Duchess of Cambridge to Sarah Ferguson to Australian-born Crown Princess Mary:
Catherine, Duchess of Cambridge, has been giving lessons in the curtsy since she officially joined the royal family in 2011. Here, she and Prince Harry greet King Philippe of Belgium in 2014.
Taking after her mum, Princess Charlotte tried out her first-ever curtsy during the royal tour of Poland and Germany in 2017.
Sarah Ferguson shows off her impressive thigh strength alongside daughter Princess Beatrice and ex-husband Prince Andrew at this year's Royal Ascot.
The face you make when the royals let you back into the fold!
Duchess Catherine is yet again the picture of poise as she bows to The Queen at the royal's 2017 Easter service.
Who could forget this moment? Joining the royal family for Christmas at Sandringham just months before her wedding, Meghan Markle showed off her first public curtsy to The Queen. While seasoned Kate led the way, Meghan's was a little more wobbly. But that's what makes us love her even more - she's just like us!
Who says men can't get their curtsy on? While royal protocol dictates only women need to perform the gesture, Zara Tindall's husband Mike gave it a go at Royal Ascot in 2015.
As is tradition, royal brides are expected to curtsy on their wedding day to The Queen. Here, Princess Diana and Prince Charles show their mark of respect to The Queen at their 1981 wedding.
In 1986, Sarah Ferguson performed the maneuvre with bridal joy.
Double act: In 2011, Duchess Catherine was assisted by her bridesmaid and sister Pippa Middleton during the historical moment.
We love this tender interaction between Sophie, Countess of Wessex and the late Queen Mother in 1995.
One present-day Queen, one future Queen: Duchess Camilla greets her mother-in-law with a curtsy and kiss.
Australian-born Crown Princess Mary is a total curtsying ninja!
She's practically on the ground as she welcomes Queen Maxima of the Netherlands to Denmark in 2015.
Sophie, Countess of Wessex, and Princess Michael of Kent show us how it's done.
Former ballerina Princess Diana had the royal cursy mastered! (L-R) Princess Diana curtsies to The Queen at the funeral of her father, Earl Spencer, in 1992 and the Princess of Wales greets King Juan Carlos of Spain, who kisses her hand, in 1987.
The award for most enthusiastic royal curtsy has to go to Sarah Ferguson.
The affection between Princess Mary and her mother-in-law Queen Margrethe II of Denmark was on show at Crown Prince Ferderik's 50th birthday celebrations in May.
Prince Charles and Princess Diana with Prince Juan Carlos and Queen Sofia during the royal tour of Spain in 1987.
Princess Eugenie spices up her curtsy with a wave - but we're not sure whether The Queen can even see her!
Just like her mum, Princess Beatrice pulls off a strong and low bob.
The politics behind the curtsy: Duchess Catherine may one day be Queen, but according to The Telegraph in the UK, in 2012 the Queen updated the rules and Kate must curtsy to "blood princesses" including Princess Royal, Princess Alexandra, and the daughters of the Duke of York, Princesses Beatrice and Eugenie, who are actually below her in the royal social order because of her marriage to Prince William.
This rule does not apply if she is joined by Prince William.
But Catherine must always curtsy to Duchess Camilla, Prince Charles, The Queen and Prince Philip.
Whatever you think of the tradition, it's certainly fascinating to watch it in action!