VERO BEACH, Fla. -- It has been 12 years since Hall of Famer Ken Griffey Jr. made one of the most impactful uniform changes in sports history.

On April 15, 2007, Griffey Jr., then a Cincinnati Red, ran onto Chicago’s Wrigley Field donning a No. 42 jersey instead of his No. 3. Griffey Jr. was honoring Jackie Robinson, who broke Major League Baseball's color barrier 60 years prior.

Griffey Jr.’s personal decision stirred a league-wide movement. Two years later, Major League Baseball began requiring all its uniformed personnel to wear 42 on Jackie Robinson Day.

Now, Griffey Jr.’s back to inspire young players at the very place Jackie Robinson grew his legend: the Jackie Robinson Training Complex, formerly known as Historic Dodgertown, where Robinson spent Spring Training with the Brooklyn Dodgers.

Major League Baseball and the MLBPA are hosting Griffey Jr. as part of the fifth annual Hank Aaron Invitational, where 130 diverse high school ballplayers from across the country are developing their skills.

“This is a rare opportunity that you guys are fortunate to have,” said Griffey Jr. to the attendees, who were visibly awestruck of the 13-time MLB All-Star standing at the podium ahead of them.

Over two dozen former MLB coaches and players, including two-sport star Brian Jordan, are joining Griffey Jr. in Vero Beach to share their elite baseball knowledge with the next generation.

And some of those lessons extended off the field. For instance, Griffey Jr. emphasized to the players the importance of staying away from trouble-making friends and negative social media use.

“Keep your nose clean, do things the right way, because we’re all rooting for you,” he said. “There’s not one person up here that doesn’t want to see you guys in the big leagues. We honestly and truly love this game and want this game to be the best game.”

Over the week, the players are learning how to manage the rigors of a Major League schedule. The Hank Aaron Invitational is structured like an MLB Spring Training program, with meetings, games and group meals slotted at specific times each day.

Being the son of Ken Griffey Sr. -- a three-time MLB All-Star -- Griffey Jr. was accustomed to that highly regimented lifestyle before Seattle drafted him No. 1 overall in 1987. But for those who aren’t, Griffey Jr. is ready to get them up to speed.

“I’m helping you guys,” Griffey Jr. said. “We didn’t have that growing up, but you guys have that. So, it’s important for you to get your work in, learn from these guys, take it back and build on it.”

Griffey Jr. spent over 30 minutes taking questions from the players. Some asked him how long he worked on his swing -- "every day," he answered -- and others wanted to know things like his favorite moment in the big leagues. They were questions the Hall of Famer has likely heard before, but he obliged, with a smile, anyway.

One question, however, lit his eyes up.

“Why is baseball cool?” Griffey Jr. asked, repeating the player’s inquiry. “That’s a very simple question -- because it’s the best game. It doesn’t matter how big you are or how small you are.

“You see all types of shapes and sizes, but right here,” he said, pointing to his chest. "That’s what means everything.”