Little is known about the way Shou Zi Chew, 40, operates or even how much power he truly holds at the company as its CEO.
Chief operating officer Vanessa Pappas has been the public face of TikTok, and was grilled by Congress last September about US data flows to China.
A New York Times profile last September, citing former TikTok and ByteDance executives, also suggested that Chew's ability to make decisions is limited, and that ByteDance founder Zhang Yiming holds the reins at the company.
But TikTok is now putting Chew front and centre publicly, at a time when TikTok's connections to the Chinese government are under great scrutiny.
In a letter to lawmakers last June stressing that it operates autonomously of parent company ByteDance, the company took pains to note that he is not from China but "a Singaporean based in Singapore".
Committee chairwoman calls for outright ban of TikTok
Chairwoman Cathy Rodgers has started the hearing with scathing criticism of TikTok.
The Republican congresswoman says the US should ban the platform for a variety of reasons, saying it threatens innocent children and poses a threat to national security because of TikTok's Chinese owner ByteDance.
Rodgers says it promotes mental health issues in young people and facilitates drug dealers.
She adds that the US government must be prepared to ban any platform the Chinese government might use to track American citizens.
TikTok CEO defends platform's safety
Shou Zhi Chew has begun a spirited defence of TikTok, making the case for possible benefits to children and young people in the form of educational videos.
Videos about STEM (science, technology, engineering, and mathematics) topics have been watched more than 116 billion times on the platform, he says.
He adds that TikTok takes national security concerns very seriously, adding that ByteDance is "not owned or controlled by the Chinese government", with 60% of its shared owned by global investors and three of its five board members form the US.
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