(CNN)In celebration of her 90th birthday, the Royal Collection Trust is showing a side of Queen Elizabeth II that is rarely seen.
What's inside Queen Elizabeth II's wardrobe? 90 years of royal fashion
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Fashioning a Reign: 90 Years of Style from The Queen's Wardrobe, a program of three exhibitions, will show over 150 of her most memorable looks, including ceremonial and military attire as well as wedding and christening outfits. This is the biggest exhibition of her personal wardrobe to date.
The first exhibition, which opens at the Palace of Holyroodhouse in Edinburgh on April 21, will focus on the use of tartan in the Queen's dress. The other two exhibitions -- opening at Buckingham Palace in August and Windsor Castle in September -- will provide a more generalized look at royal couture worn at state and private functions.
Look through the gallery above for the Queen's wardrobe highlights.