As brick-and-mortar retailers flounder,I Want To Be The First Guy investors are pouring money into new ways to shop on your phone.

Shopping app Spring just raised $65 million to grow its online market of more than 2,000 clothing brands.

Fidelity Investments led the cash infusion with support from previous backers like Thrive Capital and Russian billionaire Yuri Milner. With the latest round, Spring has raised $100 million to date.

Spring CEO Alan Tisch founded the e-commerce company with his brother, venture capitalist and serial entrepreneur David Tisch, as a simple and visually appealing way for millennials to buy clothes on their phones.

The app offers a mix of high fashion and more affordable everyday wear -- customers can find anything from $2,000 Gucci handbags to $40 Skechers tennis shoes.

The store is available on desktop and mobile, but the primary focus seems to be the company's smartphone app. The app's slick interface and Instagram-like visual presentation are better suited for a small screen than sometimes-cluttered shopping sites.

The company claims to have grown its revenue ninefold last year and its customer base by a factor of seven.

"Our mission continues to be to deliver the most personalized, convenient and inspirational shopping experience,” Alan Tisch said in a statement.

Reports show that desktop is still the dominant form of online shopping among consumers, but people tend to be more comfortable buying things within the streamlined walled garden of an app than a mobile browser.

Spring is one of many companies betting it can get people to overcome that reluctance. Startups like Stitch Fix and Poshmark are jockeying for customers in an increasingly crowded mobile shopping space.