Turning back the clock, Serena and Venus Williams will clash in a grand slam title decider for an incredible ninth time after scoring contrasting Australian Open semi-final triumphs.
Venus needed almost two-and-a-half hours on Thursday to see off CoCo Vandeweghe 6-7 (3-7) 6-2 6-3 to become the oldest women's finalist in professional tennis history, before Serena crushed Croatia's Mirjana Lucuc-Baroni 6-2 6-1 in a commanding display.
"It is definitely 100 per cent the best-case scenario that I could have ever dreamt of," Serena said.
"I just feel like it's been a while. This probably is the moment of our careers so far. For me, I can definitely say for me.
"I never lost hope of us being able to play each other in a final, although it was hard because we're usually on the same side of the draw.
"Whenever we're on the opposite side, I always definitely feel a lot better."
The all-conquering sisters last squared off for a grand slam crown at Wimbledon in 2009, when Serena prevailed 7-6 (7-3) 6-2.
At 35, Serena leads 36-year-old Venus 6-2 in matches played on tennis's four grandest stages and another victory at Melbourne Park - in a repeat of their 2003 final - would give her an unprecedented seventh Australian Open singles title.
"For us to both be in the final is the biggest dream come true for us," Serena said.
"I was really proud of Venus. She's another total inspiration, my big sister.
"She's basically my world and my life. She means everything to me and I was so happy for her obviously."
Serena also shares the open-era record of 22 majors with Steffi Graf but can surpass the great German on Saturday and draw to within one of Margaret Court's all-time benchmark of 23 grand slam singles titles.
Serena can also regain her world No.1 ranking - which she has held for a total of 309 weeks - if she dethrones defending champion Angelique Kerber, who crashed out in the fourth round.
But the second seed is taking nothing for granted ahead of what will be her 29th grand slam final.
"She's my toughest opponent. No one's ever beaten me as much as Venus has," Serena said.
"I just feel like no matter what happens, we've won.
"She's been through a lot. I've been through a lot. To see her do so well is great so I look forward to it."
Despite being in the twilight of their careers, the recently engaged Serena is refusing to rule out the sisters setting up a 10th all-Williams grand slam final showdown down the track.
"Never say never," she said. "Look at us now."
Williams v Williams finals
2001 U.S. Open - Venus won 6-2, 6-4.
2002 French Open - Serena won 7-5, 6-3.
2002 Wimbledon - Serena won 7-6 (4), 6-3.
2002 U.S. Open - Serena won 6-4, 6-3.
2003 Australian Open - Serena won 7-6 (4), 3-6, 6-4.
2003 Wimbledon - Serena won 4-6, 6-4, 6-2.
2008 Wimbledon - Venus won 7-5, 6-4.
2009 Wimbledon - Serena won 7-6 (3), 6-2.
Career grand slams:
Serena 22 (Australian Open 6, French Open 3, Wimbledon 7, US Open 6)
Venus 7 (Wimbledon 5, US Open 2)