1:14 p.m. | Updated With interview with third student.

Mimi Yen's father thought she was just playing with worms. But Ms. Yen’s countless hours spent in New York University’s Center for Genomics and Systems Biology lab over two years was far from play.

Her experiments with worms shed light on how genes control behavior. And her work earned her a place as a finalist in the Intel Science Talent Search. Ms. Yen, 17, is one of three New York City students chosen among 40 finalists for the nationwide competition.

A fellow Stuyvesant High School student, Huihui Fan, 17, from Staten Island, studied how to genetically improve the shape of crop plants’ roots.

A third New York City student, Danielle Goldman, 17, studied anxiety disorders among young people. Ms. Goldman is a Bronx High School of Science student.

The high school seniors, chosen from 1,839 applicants, will head to Washington for the final round of judging for the prestigious science award. The grand prize winner of the $100,000 scholarship will be announced March 13.

Both Ms. Yen and Ms. Fan joined a team at Stuyvesant in their sophomore year to design a "bionic" eye for the Toshiba Exploravision Contest. They were supervised by Dr. Jonathan Gastel, their science teacher. “They became National Finalists,” wrote Dr. Gastel in an e-mail message. “They were curious, creative and committed.”

Dr. Gastel, who heads Stuyvesant's research program, has helped six students who went on to be finalists over the last five years.

All three students agreed to talk about their projects and their scientific journey.

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Mimi Yen

Mimi Yen knows how strange her research might seem to non-scientists, especially classmates, so she doesn’t go into it. Worm sex habits and their hermaphrodite tendencies are hardly high school chatter. “It’s awkward,” she says.

There were a lot of times, she said, when she just wanted to give up. "But I had a lot of support," she said.

Ms. Yen immigrated from Honduras with her parents when she was five. The family arrived in Queens, where Ms. Yen attended Public School 102 and then Intermediate School 73.

When her family moved to Williamsburg, Brooklyn, Ms. Yen finished middle school at I.S. 318 before entering Stuyvesant High School.

Ms. Yen's mother works in a garment factory and her father in a restaurant. She said they don't speak much English -- neither finished high school -- but they support her in many ways. They waited for Ms. Yen to return from the lab to have dinner together at home -- which was sometimes past 9 P.M. They encouraged her to get more sleep.

The worm research started two years ago in Ms. Yen's sophomore year. She had heard Dr. Matthew Rockman, assistant professor of biology at New York University, give a presentation about his work. But Dr. Rockman's genomics lab was just getting started and he was wary about letting in a high school student.

"Even working with undergrads is not a sure thing," said Dr. Rockman. But Ms. Yen convinced Dr. Rockman she was serious.

Every school day, Ms. Yen had a class called Intel Research, a ticket to leave school at about 3 p.m. and head straight to Dr. Rockman's N.Y.U. lab in Greenwich Village.

On week days, and some weekends, Ms. Yen spent up to 30 hours a week studying C. elegans, a worm species whose genome is fully sequenced. Two summers were completely devoted to the research.

“She did experiments against my intuition,” said Dr. Rockman. “She’d follow her own instincts and it turned out she was often right.”

Huihui Fan

Two floors above Ms. Yen, her classmate, Huihui Fan, also worked in the Center for Genomics and Systems Biology. In Dr. Gloria Coruzzi's lab, Ms. Fan researched genes that determine the shape of crop root structures.

The Fan family left China when Ms. Fan was three, with stops in Vancouver, Canada and Philadelphia, where Ms. Fan attended Coopertown Elementary and Haverford Middle School.

Ms. Fan's mother worked at Thomas Jefferson Hospital in Philadelphia researching HIV. Ms. Fan accompanied her to the lab after school. She remembers sitting and watching the researchers at work.

Later, as the captain of the Stuyvesant debate team, Ms. Fan argued about overuse of pesticides and the issue stuck with her.

"If plants roots could be wider and longer, crops could access more nutrient rich soil, and farmers could use less pesticides," said Ms. Fan in a phone interview.

In the fall, Ms. Fan said she'll head to Harvard to study biochemistry.

Danielle Goldman

Danielle Goldman loves children, especially troubled ones around her own age. For two and a half years, Ms. Goldman studied 12- to 19-year-olds, who struggled with depression and anxiety. Her findings could lead to improvements in the way troubled youths are helped at the molecular level, through a brain chemical called GABA.

Ms. Goldman, a senior at the Bronx High School of Science, was born and raised in Astoria, Queens. She attended P.S. 166 Henry Gradstein or elementary school and then P.S. 122 Mamie Fay, The Academy for the Intellectually Gifted.

At Bronx Science, Ms. Goldman's work grew out of a course called Social Science Research. The goal was to build a relationship with an active research lab. Dr. Zach Lynn, her teacher in that three year course at Bronx Science, helped Ms. Goldman focus her interest and connect with a mentor.

Ms. Goldman is thankful for teachers like Dr. Lynn. "Teachers have not only taught me their specified subject matter, but they have taught me the love of the subject," Ms. Goldman wrote in an e-mail message.

During the school year, Ms. Goldman traveled an hour to reach the New York University Child Study Center in the East Village. The lab is run by her mentor, Dr. Vilma Gabbay, assistant professor of psychiatry at N.Y.U.

The young scientist investigated data collected by the lab, said Benjamin Eli, a research assistant who worked with Ms. Goldman. She dedicated up to 12 hours a week after classes, starting as a sophomore, plus two summers.

Ms. Goldman said her father, an art dealer, and her mother, a homemaker, don't pressure her.

She will stay in New York City at Columbia with plans to focus on neuroscience. Her goal is to continue to medical school and pursue a career in pediatric and adolescent psychiatry.

One day, Ms. Goldman just might use her own research to treat children.

She wrote, "In addition to seeing patients, I hope to conduct further research to better society by aiding children in need."