In this pic (source: hola) is Her Majesty the Queen Elizabeth II wearing the miniatures of her parents? I am sure one is King George VI, but I'm not sure if the other is herself or the late Queen Elizabeth the Queen Mother?
And one more question: What is the name and history of the tiara?
I think the tiara question has been addressed, so I'll discuss the miniatures. They are awards from the Royal Family Orders of various sovereigns.
The Royal Family Order is a personal memento issued to female members of the family, usually as a thank you for their service to the monarch. The custom is to wear the most recent one towards the top. Queen Elizabeth II wears the order of her father, George VI, and her grandfather, George V. So that would be her grandfather in that second one with the blue ribbon.
Queen Alexandra had her own personal order that she bestowed upon those in her service, but it was an unofficial order. Queen Elizabeth the Queen Mother did not have an order of her own. She wore the order of her daughter, her husband, and her father in law.
It's also interesting to note who receives the Queen's order and who doesn't. Diana received one, but Sarah, Duchess of York did not. Camilla and Sophie have both received it, as well as Zara Phillips. The Duchess of Kent and Gloucester have it as well, as does Princess Alexandra. Princess Michael of Kent does not have it.
It's not something that gets announced, either, so the only way to see who has it is to see who is wearing one at formal events.
ETA: Whoops! When I started digging a little deeper to see if there were photos of Zara wearing the order, I found that Wikipedia lied to me!