The husband and wife designer duo Sachin and Babi Ahluwalia did something radical a year ago that changed the course of their business journey altogether—they really listened to their clients. That one seemingly simple action brought amazing rewards with it: a massive spike in their e-commerce business and major celebrities wearing their creations to big-ticket red carpet events. Last week, this list gained another iconic new member when Michelle Obama made a surprise appearance at the 61st Annual Grammy Awards in a decadently sequinned Sachin & Babi pantsuit.

The spark that lit this flame was feedback from a section of the population that has historically been underserved and underrepresented by fashion houses world over. Curvier fans of the label wanted it to produce its elevated occasion wear in larger sizes. When the messages kept coming in from several quarters, the designers went back to the drawing board, reworking their sketches, patterns and fabrics to better serve a ready and waiting army of women who wanted chic ready-to-wear crafted from lush fabrics for special occasions, just like their straight-sized counterparts.

Today, a majority of styles Sachin & Babi design go from size two to 20, and can be shipped to any corner of the globe. And as their size offerings expanded, so did their relationships with Hollywood's stylists, who often struggle with finding designers to dress curvier celebrities. Sachin & Babi's robust red carpet roster now includes names like Octavia Spencer, Patricia Clarkson, Mindy Kaling, Chrissy Metz, Laurie Metcalf and Brooke Shields, among others.

Over coffee at the label's atelier in the heart of New York's Garment District, Sachin and Babi Ahluwalia talk about sizing, inclusivity and authenticity, and how they navigated the past year that culminated in a triumphant awards season moment with the former First Lady of the United States. Edited excerpts below.

What first compelled you to extend your size range?

Babi Ahluwalia: Honestly, [the catalyst] was the girl. She reached out to us from all across the universe—via emails, direct messages on our social channels and left feedback in our store. The same message came from my girlfriends, consumers, stylists and influencers—“Make this in my size.”

Sachin Ahluwalia: We've also been called out by clients, like the one who loves our brand and buys our clothes but felt [alienated by the fashion show] seeing six feet tall, size zero models walk the runway. She told me to fix our website and make sure it represented women like her. That really resonated with me. That day, we decided to take our money away from shows and put it into the site, into infrastructure to add sizes, and to communicate our brand message.

What did you have to change technically to be able to widen your size range?

SA: The challenge for creating silhouettes that work from size two to 20 is obviously the fit. The biggest problem that happens when designers get to bigger sizes is they change the pattern, or charge more because they're using more fabric. To me, that wasn't right. We went back to the initial sketching process to find silhouettes that could transcend from size two to 20. We spoke to a lot of our friends to get a better understanding of what their needs were. Then, we worked intensively with our technical pattern-makers and fit model. Our objective is to give size two and 20 the same fit and experience. It does take time; it took us a whole year to refine it.

We both truly believe in diversity, but everyone doesn't hear our voices every day. The brand and the product have to speak, so we redid our website as well. We stopped shooting e-commerce [images] on a size zero [bodies]. We now shoot on a model between a size four and six, and shoot the same dress on a model who's size 14.

Non-sample-sized celebrities have often spoken about how difficult it is to find designers to dress them for red carpet events. Was working with curvy celebrities part of your larger push for diversity?

SA: We've been on the threshold for inclusivity for a while now. Chrissy Metz's stylist came to us two years ago, but at that point we weren't [selling] sizes 16 or 18. We don't want to dress a celebrity as a one-off and not produce that size for regular clients. It's not authentic. Once we started doing the pivot and added extended sizing, we welcomed stylists dressing curvier celebrities. We've had a genuine response from stylists in Hollywood.

BA: In terms of diversity, it's not necessarily based on size. We took on ageism. [For a recent campaign] we had 70-year-old Maye Musk. It has to be diverse: you need young girls and more established names; you need extended sizes and straight sizes. It has to reflect the world and the people in it.

How did the Michelle Obama Grammys moment come about?

BA: It was not really intended for the Grammys. I got a call from Meredith Koop [Obama's stylist] a couple of weeks ago. She said she had been noticing the brand and would love to work with us for Mrs Obama's book tour. She picked a couple of soft, leisurely pyjama suits from the pre-fall [collection]. I asked if I could surprise her, and she agreed, saying Mrs Obama loved jewel tones. Since this was our first outfit for her, I wasn't really feeling a print. I had these beautiful loden green sequins, so I whipped up a sketch with them in mind. I sent Meredith the sketch, and she said it looked beautiful. We made it and shipped it in ten days. I got an email the Thursday before the Grammys saying the fitting went fine, but that it may not be for the book tour and that she was going to do something special with it.

SA: Which is often code for it's probably not going to happen.

BA: On Sunday, we did our Whole Foods run and came back home to text messages telling us to turn on the TV, and there she was!

SA: We got such a great response from everyone. A moment like this really moves the needle for a brand like us. You can hope for it, but there's no way you can orchestrate it.

Also read:

What you need to know about designers Sachin & Babi's take on inclusivity

7 reasons the Sachin & Babi presentation at New York Fashion Week was unmissable

Sachin and Babi bring New York and Goa together