Some tennis moments will stay in the mind as parts of history.
Examples that spring to mind are Andy Murray winning Wimbledon for the first time, and Cori Gauff being the youngest player to qualify for Wimbledon since it became professional.
But for people who have played tennis at the top of their game, it can be extremely difficult to pick individual moments that stand out as a highlight.
That was certainly the case for some of these former pros.
This article was published in July 2019
How to become a professional tennis player. video
Legends of the game with advice for the champions of tomorrow.
What's it like to be a ball girl or boy at Wimbledon?
The training and discipline required to be a valuable part of the tennis championship.
How many miles do we run during a tennis game?
Tennis is more than just hitting a ball - find out how much running is involved in a game.