Tennis superstar Serena Williams on Wednesday announced that she has quietly been building a venture capital portfolio since 2014, amassing investments in more than 30 start-ups with an accumulated market cap of $12 billion.

Williams announced this via her Instagram account to her 11 million followers. In a post, she admits, "Yes, I know I can keep a secret." 

The winner of an Open Era record 23 grand slam singles titles, Williams, who serves as president of Serena Ventures, said she launched the investment company with the mission of giving an opportunity to founders across an array of industries that embrace diverse leadership, individual empowerment, creativity, and opportunity. 

“As we grow, we hope to mentor young founders and take burgeoning entrepreneurs to the next level. We have so many exciting things coming up,” said wrote on her website. 

Her VC firm helps forge relationships for founders, encourages collaboration among portfolio companies, and expands partnership opportunities across her network. Among its portfolio companies are blockchain exchange coinbase, education platform masterclass, on-demand fitness training platform tonal and nutrition company Olly.

Serena Williams continues to break new ground in technology and investment. Williams is among many top-tier athletes that have partnered with VCs, launched their own investment companies.