Hailey Bieber tests Rhode products on her husband Justin Bieber

Speaking to WSJ. Magazine's Innovators Issue, Hailey explained: "I test them on my husband, I test them on my friends. I'm product-obsessed."

Hailey has enjoyed huge success with Rhode, and the model explained why she decided to launch her own company, rather than working with an existing brand.

Hailey - who has been married to Justin since 2018 - shared: "I had lent my name enough times to see how it benefited that company. I knew for a fact that if I'm doing this, I have to be the majority owner."

Earlier this year, Hailey announced that she was selling her beauty brand in a deal worth up to $1 billion.

The model confirmed that she was selling Rhode to e.l.f. Beauty after reaching an agreement with the cosmetics company.

Hailey - who is remaining with the company as the chief creative officer - said in a statement at the time: "From day one, my vision for Rhode has been to make essential skin care and hybrid make-up you can use every day.

"Just three years into this journey, our partnership with e.l.f. Beauty marks an incredible opportunity to elevate and accelerate our ability to reach more of our community with even more innovative products and widen our distribution globally."

Meanwhile, Tarang Amin, the CEO of e.l.f. Beauty, confessed to being impressed by Rhode's growth in a relatively short period of time.

The e.l.f. Beauty boss admitted to being shocked by the sudden rise of the Rhode brand, explaining that the "level of disruption" caught his attention.

He told CNBC in May: "I've been in the consumer space 34 years, and I've been blown away by seeing this brand over time. In less than three years, they've gone from zero to $212 million in net sales, direct-to-consumer only, with only ten products. I didn't think that was possible.

"So that level of disruption definitely caught our attention."