When Prince William proposed to Kate, she was given the sapphire and diamond engagement ring that once belonged to Princess Diana.
It has a 12-carat oval blue Ceylon sapphire which is surrounded by 14 diamonds.
On their big day, Kate walked down the aisle wearing the Cartier Halo Tiara, which was borrowed from the Queen.
Since the wedding, Kate has donned other eye-catching jewels from the royal collection.
She is also happy to display pieces from her private jewellery collection when stepping out.
Earlier this year, Kate started wearing a gold pendant that had a sweet dedication to her family.
The Duchess of Cambridge was spotted with a long gold chain necklace that had a circular pendant on it.
The style of jewellery has a link to her children, according to Claire Adler, jewellery specialist and founder of Claire Adler Luxury PR.
Speaking to Express.co.uk, she said: “Initial pendants are a super personal style of accessory and are often worn as a way to celebrate one’s children or other beloved family members.
“A longer necklace allows the wearer to see and remember the pendant and it’s symbolism at all times.
“This pendant worn by Kate is the gold diamond midnight moon necklace from Daniella Draper, personalised with the initials of Kate’s three children, with G, C and L proudly referring to Prince George, Princess Charlotte and Prince Louis.
“The moon charm on the pendant represents immortality, eternity and enlightenment.”
The necklace allows Kate to keep her family close to her when she is out at official engagements.
The design of the piece also shows Kate’s support of British bands and sustainability, the expert continued.
“It is made with 100 percent recycled nine carat gold,” she added.
“This suggests that sustainability is important to Kate, as well as supporting independent, family run British brands.”
While Kate is sure to have access to any jewels that she wants, the royal shows her family side by picking the personalised pendant.
The expert explained wearing this can also help her express her own individuality.
Claire added: “Initial necklaces are increasingly popular because they are a way of expressing individuality and also they can carry meaning for the wearer and potentially also a person who gifts the jewel.”