Kiki Bertens of the Netherlands, Sloane Stephens of the United States, Naomi Osaka of Japan, Angelique Kerber of Germany, Caroline Wozniacki of Denmark, Petra Kvitova of the Czech Republic, Elina Svitolina of the Ukraine & Karolina Pliskova of the Czech Republic take a selfie during the iconic photo shoot for the 2018 WTA Finals tennis tournament