Naomi Osaka saved two match points and Serena Williams was taken to three sets as two of the favourites reached the Australian Open quarter-finals.
Having lost the opening set to Garbine Muguruza, Japan's Osaka was a break down in the second and faced two match points at 5-3 in the third.
But she won four games in a row to win 4-6 6-4 7-5 against the Spaniard, who is also a former world number one.
Williams then came through 6-4 2-6 6-4 against Belarusian Aryna Sabalenka.
The American surged into a 4-1 lead in an entertaining final set, before 22-year-old seventh seed Sabalenka broke back and levelled at 4-4.