United Kingdom, Sept. 4 -- Serena Williams has joked "Mama's always watching" after her daughters Olympia and Adira found themselves surrounded by giant photographs of their tennis superstar mother during a shopping trip to Nike.

The tennis icon, 44, shared pictures of Olympia, nine, and Adira, three, posing beside new and huge black-and-white images of her playing tennis at a Nike store.

The family moment came during Serena's remarkable return to competitive tennis at the US Open, where she has already played mixed doubles alongside Carlos Alcaraz, and is preparing to reunite with her sister Venus Williams in the women's doubles.

Posting the photographs of her daughters on Instagram, Serena joked: "@olympiaohanian and @adiraohanian to...