In 1964 came the documentary Seven up, which followed 14 British children with different class backgrounds.
There was nothing special about it, really, but seven years later Michael Apted, who had been involved in selecting the 14 children, took over and made a sequel called 7 plus seven.
Every seven years that followed, an interview was conducted with interviews with those who agreed to continue.
21 Up was followed by 28 Up and so on.
The documentary series has examined how the main characters' lives have continued, based on their class background and life's tours, which include working life, marriage, divorce and celebrity.
The latest movie was 63 Up which came in 2019.
Directed James Bond film, Narnia and Loretta Lynn biography
Michael Apted was told by one of the female participants that he asked women about home life and romance, while the men were allowed to talk about religion, philosophy and career.
According to Variety, there was something that influenced the director when it came to the choice of films.
Among other things, he made the biography film about Loretta Lynn (Coal miner's daughter), The Gorillas of the Misty Mountains and Enough.
His list of films also includes the James Bond film The world is not enough and the Narnia film Caspian and the ship Dawn.
It remains to be seen what happens to the documentary series Up after Michael Apted passed away.
But the series has followed many followers in several countries that are still going on today.
Michael Apted turned 79 years old.