Gain unprecedented access into their lives of the extraordinary tennis sisters Venus and Serena Williams, and their most intimidating year of their career.

Ever since Venus and Serena Williams started playing in tennis tournaments, they’ve provoked strong reactions – from awe and admiration to suspicion and resentment. They’ve been winning championships for over a decade, pushing the limits of longevity in such a demanding sport. How long can they last?

Over the course of 2011, Venus grappled with an energy-sapping autoimmune disease while Serena battled back from a life-threatening pulmonary embolism. Neither Venus nor Serena let their adversities hold them back. They drew their greatest strength from each other.