(AZ Central) -- Girl Lego builders can now use three female scientists as their protagonists in a new set so popular it is already out of stock.
The 165-piece Research Institute features a female paleontologist, chemist and astronomer. The box cover shows them mixing chemicals in a lab, building a T-Rex model and peering through a telescope.
Lego lovers can still purchase the $19.99 set, but there is a 30-day wait, according to customer service representatives. It was released Aug. 1.
Could the new female figures be a response to the scathing letter -- which went viral over social media -- written by a 7-year-old girl?
"I love Legos," Charlotte Benjamin wrote in a note that was re-tweeted more than 3,000 times.
She complained that the girl toys were, well, very girly.
"All the girls did was sit at home, go to the beach, and shop, and they had no jobs but the boys went on adventures, worked, saved people, and had jobs, and even swam with sharks."
Lego responded that is developing new male and female figures.
Coincidentally, the hugely popular "The Lego Movie" was released in February, about a month after Charlotte's passionate plea.
It turns out that one of the key characters is the beautiful yet capable rebel Wyldstyle, who despite being Batman's girlfriend, saves Emmet from Bad Cop.
The Research Institute set follows other recently created female Lego characters, such as a surgeon and astronaut. Last year, Lego produced its first female scientist, a character who could attach new pieces to minifigures that lost their legs.
"Building with Lego bricks fosters the creativity of children, which is why it's our mission to offer any child - regardless of their age, gender or interests - a relevant Lego experiences."
On the shop.lego.com website, Lego says, "the Research Institute has everything that you need to explore the world below, around and above us! Created by real-life geoscientist, Ellen Kooijman... this collection of scenes depicts three varied professions within the world of natural science.
"Help the paleontologist study the origin of dinosaurs with the magnifying glass, map the skies with the astronomer and her telescope, and assist the chemist as she carries out experiments in her lab."
Lego also reported Monday that at least two other sets, the Lego Volvo Loader and Exo Suit, were also out of stock after an Aug. 1 release. They, too, can be back ordered here.
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