Claudia Sheinbaum, the former city mayor who will take office on Tuesday as Mexico's first woman president, is an environmental scientist and dedicated leftist known for keeping a cool head in times of crisis.

Sheinbaum, 62, is a close ally of outgoing President Andres Manuel Lopez Obrador, but considered more pragmatic and less populist.

"The driving force of both is the fight for a more just society, but with important nuances," analyst and author Jorge Zepeda Patterson wrote in his latest book "Presidenta."

While Lopez Obrador hails from rural southern Mexico, "Sheinbaum comes from an intellectual university environment, middle class, cosmopolitan, modern and essentially urban," he added.

She has a "more modern left" agenda that includes the issues of feminism and the environment, according to Zepeda Patterson.

Sheinbaum was born to Bulgarian and Lithuanian Jewish migrants in Mexico City during the turmoil of the early 1960s, when students and other activists were seeking to end the Institutional Revolutionary Party's long grip on power.

"I am a daughter of 1968," she often repeats in reference to the student movement.

Her mother, renowned biologist Annie Pardo, lost her job as a university professor for denouncing the massacre of students.

"At home, we talked about politics morning, noon and night," Sheinbaum was quoted as saying in a biography.

Guillermo Robles, a former classmate at the prestigious National Autonomous University of Mexico, remembers Sheinbaum as a serious student.

"Neither she nor I were that into socializing with everyone," he said.

Sheinbaum's magnetism as a young woman lay in her left-wing political convictions, Robles said.

She spent several years as a researcher in California, where she honed her English language skills.

Earthquake, metro collapse

In 2000, Lopez Obrador, then the newly elected mayor of the capital, appointed Sheinbaum as Mexico City's environment secretary, with an agenda to reduce pollution.

She returned to academic life after Lopez Obrador's defeat in the 2006 presidential election.

Sheinbaum was a contributing author of the United Nations' Intergovernmental Panel on Climate Change that won the Nobel Peace Prize in 2007.

In 2017, after she returned to politics, Sheinbaum faced criticism when a powerful earthquake caused a school to collapse in a southern Mexico City district where she was the local mayor, killing 26 people, including 19 children.

Sheinbaum denied that irregularities in the construction were her office's responsibility, and went on to be elected mayor of all of Mexico City the following year.

Her use of scientific methods and technological tools was seen in the Covid-19 pandemic response in the capital, though it did not prevent a high mortality rate.

"She has an impressive capacity for analysis, reading data and finding very practical solutions," said Tatiana Clouthier, a former economy minister who was a spokesperson for her election campaign.

"Despite being a scientist, she is something of a social fighter, which makes a very good combination of heart and mind," Clouthier added.

In 2021, while Sheinbaum was Mexico City mayor, disaster struck again when a section of elevated metro track collapsed, killing 26 people and injuring dozens.

Sheinbaum rejected accusations that budget cuts were to blame.

She negotiated with the construction company owned by business magnate Carlos Slim that built the line to obtain compensation for victims and avoid lawsuits.

"Governing is about making decisions. You have to make a decision and assume the pressures that can come from it," Sheinbaum said.

During a series of heated debates before the June election, Sheinbaum's main opponent Xochitl Galvez branded her "cold and heartless," saying she lacked sympathy for child cancer patients and earthquake victims.

"I would call you the ice lady," Galvez said.

Sheinbaum remained unflappable and also showed a warmer side at times during the campaign, kissing and hugging supporters, and revealing a nerdy sense of humor in TikTok videos.

She shared videos with the news of her marriage in November 2023 to her university sweetheart, Jesus Tarriba.

Robles, her former classmate, said success had never gone to her head.

"She does have love for Mexico. She's not ambitious like many politicians. Claudia is not even remotely like traditional politicians," he said.