Reigning Wimbledon champion Serena Williams was hailed as an inspiration by sister Venus as she prepared to continue an emotional title defence.
Williams is playing only her second tournament since recovering from a serious foot injury and blood clots on the lungs, which left her in fear of her life.
The 13-time grand slam champion broke down in tears after beating Aravane Rezai 6-3 3-6 6-1 in the first round on Tuesday.
Williams faces the Romanian Simona Halep on Court Two at mid-day, with Venus in awe of her strength of character.
"I think she showed (against Rezai) that once you're a champion, you're always a champion as long as you're always willing to believe in yourself," said Venus.
"I think she a good role model for anyone. It means a lot to her to be back.
"I don't think anybody else will ever understand what she's been through.
"As a family we always stayed positive. When times get tough, we always laugh. She stayed positive and I think a lot of people could have got negative."
Venus Williams has also been sidelined for most of the year, with a hip injury, but she navigated through a "perfect storm" to beat veteran Kimiko Date-Krumm and reach the third round.
While rain fell outside, Williams and Date-Krumm entertained the Duchess of Cornwall and the Centre Court crowd under the closed roof with some breathtaking tennis.
Date-Krumm took the first set on a tie-break but only after Williams had battled from 5-1 down and saved a total of seven set points.
Williams moved a break up early in the second set to draw level in the match before prevailing in a hard-fought third to clinch a 6-7 (6/8) 6-3 8-6 victory in nearly three hours.
The American had only played four matches since January after suffering the injury at the Australian Open and was relieved to find a way past the 40-year-old.
"I thought she played unbelievable. I thought she had some luck on her side. This is a great surface for her too," said Williams.
"It was a perfect storm for her to try to get a win. Thankfully I had some answers."
Vera Zvonareva, last year's beaten finalist, overcame Russian compatriot Elena Vesnina 6-1 7-6 (7/5) and she will meet Tsvetana Pironkova, who beat Petra Martic 6-1 6-4.
Fourth seed Victoria Azarenka cruised into the third round with a 6-0 6-3 victory over Iveta Benesova and will now face Daniela Hantuchova.
British number three Anne Keothavong crashed to a 6-2 6-1 defeat to eighth seed Petra Kvitova, who will now play Roberta Vinci.
Eleventh seed Andrea Petkovic was last on court as darkness fell but teed up a third round meeting with Ksenia Pervak after beating Canadian Stephanie Dubois 6-3 4-6 6-3.
Top seed Caroline Wozniacki and French Open champion Li Na are both in action today while title favourite Maria Sharapova meets British 17-year-old Laura Robson on Court One.
Elena Baltacha, the British number one, tackles 20th seed Shuai Peng from China.
