Cosmetic Chemist Roselin Rosario-Meléndez

Roselin Rosario-Meléndez

Dr. Roselin Rosario-Meléndez has always loved makeup, but even her younger self couldn’t have imagined that she would end up creating a best-selling lipstick as a chemist. She had never known a chemist, let alone heard of a cosmetic chemist. Being a scientist just didn’t cross her young mind. Finding her way to her career wasn’t part of a grand plan. In fact, many of the opportunities Roselin wanted to take weren’t available to her. Instead, she walked through each new door as it opened, found what she loved, and learned new things about herself along the way.

Roselin’s early memories of science weren’t in the classroom. They were on her bookshelves at home. There were Dr. Suess books and animal flashcards, but the real prize was the family encyclopedia. It took up an entire shelf and kept calling her back. She learned everything she could, staring at pictures she now knows were orbitals in the chemistry section.

Image Credit: Roselin Rosario-Meléndez

She liked school, even playing “teacher” with her three siblings with exams and homework. But her public school experience in Puerto Rico never pushed her to dive deeply into any subject. Her encyclopedias did. “I wasn’t thinking about what I wanted to do growing up,” Roselin said. “It was just curiosity and having fun.”


As Roselin reached high school, her parents encouraged her to focus on college. The question was never whether she would go to college, but to study what. And getting there took work. Roselin knew her grades were important, but she wasn’t sure they would be enough. 


She applied to be part of a special technology program as part of her plan for getting into college. Though she was excited to go to college, the University of Puerto Rico – as a public university – was the only option she could afford. She thought the technology program would give her a competitive edge to get in. But getting in also meant deciding what to study. 


Roselin considered engineering, but the only campus with an engineering program was across the island. The added expense of being so far from home took that option off the table. She focused on the campus closest to home. Chemistry had always been her favorite science, and that campus had one of the best chemistry programs. She had her plan.

Roselin Rosario in France
Image Credit: Roselin Rosario-Meléndez

Roselin didn’t just get accepted but was offered a position in an early summer research program. Unfortunately, the cost of the program made it impossible for her to take part. She was embarrassed and disappointed. “It was something I didn’t like to talk about for a really long time, because for me it was shameful,” Roselin said. “But now I’ve gotten to the point where I can talk about this. I feel like a lot of people need to hear that.” She wants young people to realize that just because they are in a tough situation today, that doesn’t mean they have any idea where they might end up tomorrow. 

Since she wanted to study science, Roselin’s family and friends encouraged her to be a medical doctor. Unfortunately, she hated blood. She thought being a dentist could be a good compromise. She started her chemistry degree with that in mind.

But the first year was a challenge. With classes in Spanish and books in English, Roselin spent her days with a dictionary open by her side. And her doubts were only made worse by her professor. Rather than asking about her struggles, the professor suggested maybe she shouldn’t study chemistry at all. But Roselin had come so far, she wasn’t going to give up.

In her second year, the professor cared more about helping the students learn than making them prove that they deserved to be there. Roselin said the professor’s way of explaining scientific concepts blew her away. Her interest grew and her grades jumped from C’s in general chemistry to A’s in organic chemistry.

When universities from the mainland US came to interview students for summer research positions, Roselin sat through many interviews. One finally said yes. An open door. That summer at Texas A&M was Roselin’s first real experience in a research lab. She loved it. Everyone was trying something new for the first time, trying to answer questions nobody had answered before. “I had a small project, but it was a huge awakening,” Roselin said. She recognized “this is what I am meant to do.”

Roselin Rosario
Image Credit: Roselin Rosario-Meléndez

Back on campus in Puerto Rico, Roselin wanted to focus on research. The director of the research program recognized her work and reached out to her about a program at the company Merck. Roselin realized she would be the only student from her school going, and she hesitated. The director explained how big the opportunity was. She recognized another open door. She took it. Once again, Roselin knew there wasn’t anything else she wanted to do. Her mentor even guided her through the process of applying to graduate school. Though her PhD focused on biomedical work on drug release, Roselin’s advisor collaborated with many companies. Some of those were cosmetics companies. Polymerization wasn’t just in the lab; it was in gel nail polish. 

Roselin thought that this might be something she could enjoy. But she hesitated and turned down her first cosmetics offer after her PhD. After two years modifying natural materials to generate ingredients, she revisited the idea again. This time she ended up at L’Oreal working in lipstick innovation. The research was fast paced and focused. The team was driven by what customers wanted and would buy. Specifically, they were looking for a long-lasting and comfortable lipstick. After a lot of formulations, Roselin finally had one that seemed to work. But just to be sure she waited a few days and did the final check – she tested it out on herself. She was right, and now that lipstick is a best-seller.


Now Roselin works in face makeup. The pace is slower and the challenges are different because they are starting formulations from scratch. She also manages a team now. Rather than working only at the bench, she helps set objectives and track progress. Roselin still loves the lab and goes back to work hands-on as often as she can. 

Image Credit: Roselin Rosario-Meléndez

Family and friendsare excited about her job and can’t seem to help but ask for special makeup wishes. She understands the urge and even has dream products of her own (like a water-based nail polish that lasts like a gel and doesn’t smell). But the work isn’t like that. It’s fascinating and rewarding, but she isn’t just playing around with whatever she wants.

Roselin wishes people looking at her work as an industry scientist, even a cosmetics industry scientist, would recognize that it’s about the work you do yourself. “It’s not about what you memorized from a book and can talk about. It’s about how you can think beyond that,” Roselin said. Grunt work and preparation are what let her problem solve when issues come up or when ingredients arrive in unexpected ways. She finds that problem solving to be both the hardest part and the most rewarding. Roselin may not know exactly what challenge she will face next, but just like every other step she has taken, she knows she will learn something new about chemistry – and herself – along the way.

Fun Facts:

  1. Favorite thing to wear to feel powerful: High heels
  2. Music that she can’t help but stop and listen to: Reggaeton
  3. If she could have an animal best friend: Golden retriever
  4. If she could collaborate with anyone from history: Marie Curie and Rosalind Franklin
  5. Unexpected hobby: Baking, especially pizzas with LOTS of onions

Click here to purchase this issue for a kid who aspires to become a cosmetic chemist.


Check out Roselin’s interview with SWE.


  • Amanda Baker, Ph.D.
    Amanda is a scholarly publishing professional and science writer. Whether writing articles for interested kids or helping researchers publish their latest books, she has a passion for communicating the latest discoveries to curious readers from college campuses to K-12 classrooms. Her academic and professional careers have pursued a commitment to lifelong learning across the academic spectrum – including a Ph.D. from Cornell’s Department of Earth and Atmospheric Science and undergraduate majors in geology, psychology, and German at Bucknell University. She loves writing for SMORE, because every issue is a chance to tell someone else's story – from physicists to podcasters, public health experts to programmers – and introduce the readers of Smore to who they are and what they do.

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.

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