Every so often, an athlete comes along who lights up sport.
In boxing in the early 60s it was a kid called Cassius Clay, who later changed his name to Muhammad Ali. He won a gold medal at the Olympics in Rome in 1960. He was 18 and turned professional soon afterwards.
Today, the individual who dazzles boxing on the world stage is Irish woman Katie Taylor. Women's boxing struggled for years to achieve Olympic status but Katie Taylor's commitment was unwavering. A pioneering Irish woman, her sporting example, her dedication and her unwavering pursuit of excellence has made her a worldwide legend in sport. Yesterday's remarkable fifth world title win is an astonishing achievement. But, for some people, it might require context.
It was nine years ago that Katie won her first major international tournament. That was the European Amateur Championships. It was a cause for celebration.
That gold medal has since been joined in the Taylor display cabinet by five more European gold medals, the last one earned in Bucharest last June.
Keeping those medals company are five European Union Championship gold medals, the first won in Liverpool in 2008. Yesterday's hard-earned gold from Korea is part of a set of five World Championship golds.
The crowning achievement for any amateur boxer is, as it was for the lad from Louisville in 1960, is an Olympic gold. And Taylor is a proud owner of one of those.
As IABA Elite High Performance boxing head coach Billy Walsh says: "Katie has achieved a sporting dominance that no other athlete in this country has."
Anyone can see how much a gold medal victory means to Katie by simply looking at her eyes when those crucial decisions are announced. Winning is what she dreams of. Winning is what she trains for. Winning is what she does.
Such continued levels of excellence are incredibly difficult to maintain. Every sports fan knows that. Boxing, in particular, is a most demanding sporting discipline.
Boxers get hurt. They absorb pain on a daily basis. They get injured. An injury effects preparation and quite often rules out competing. Yesterday morning we watched Katie box through the pain barrier with a swollen wrist and triumph.
That sort of victory, against the best of your peers, doesn't come easy. Katie has, for years now, been the boxer every boxer hopes to defeat. And still she keeps winning.
Credit must go to her coaching team, especially master tactician Zaur Antia and, of course, Katie's father, Peter Taylor, who has guided Katie's boxing career every skip, every step, every punch of the way.
Let's no forget, women's boxing was so new in Ireland when Katie began, that for years she had to travel abroad to find opponents who had the ability to test her and push her to up her skills and fitness levels.
It's one of the joys of being a boxing fan and journalist that I've been able to watch Katie Taylor's development at first hand over the last nine years.
In all that time, it's a quote from Kenny Egan that stands out. "She refuses to lose," he told me years ago in admiration about a young woman from Bray. "She wants to win a fight more than anyone else."
It's a trait she brings to the ring every day in sparring, with a work ethic and single-minded determination that humbles all who witness it.
Speaking to Peter Taylor after Katie's Olympic final, he noted: "She's had a tough career with over 150 senior international fights. Katie doesn't have club fights because there aren't the opponents."
Some said, Katie would quit the amateur code. She didn't. She's still here, winning for Ireland. And now her focus is on retaining her Olympic crown Rio.
Katie will be 30 when she travels to Brazil. A victory would set her worlds apart. But these are the special days. The days when an international athlete towers over a sport like a Colossus.
We'll be talking about them for decades. These are the days of Katie Taylor.