For the vast majority of people, their height is nothing unusual. However, if you are particularly large or small, you could be diagnosed with either dwarfism or gigantism, but the concept of being diagnosed with both over the course of your life is almost unthinkable. Almost…

As is the case with many conditions in the medical world, there are exceptions, and a man named Adam Rainer is the only man in history to have ever lived as both a dwarf and a giant. So what exactly happened to him? And how was it even biologically possible to be both?

For all the details on Rainer’s extraordinary story, check out the video below:

Born in 1899 to average-sized parents, there was nothing in Rainer’s ancestry that would have suggested he’d live to be a record-breaker.

Growing up, Rainer was particularly small, and this was a problem for him when he tried to enlist for service in World War One but was refused entry to the army on the grounds that he simply wasn’t tall enough to fight. At the time, he was just four foot four inches tall.

Anyone who measures below four feet 10 inches is classified as a dwarf.

Most people stop growing when they are in their late teens, so when Rainer was denied entry to the army at the age of 18, he probably assumed that he was destined to live his life as a dwarf – then the unthinkable happened, causing him to become a giant by the time he was 30.