Editor's note: Kelly Wallace is CNN's digital correspondent and editor-at-large covering family, career and life. She is a mom of two. Read her other columns and follow her reports at CNN Parents and on Twitter.
(CNN) -- Melissa Atkins Wardy calls it her "a-ha" moment.
There she was looking for her first sippy cup for her then 6-month-old daughter. Her choices: Mickey Mouse, Diego and "Toy Story" characters for boys, and princesses -- and more princesses -- for girls.
Already fired up, she walked through the toy aisles and saw what she describes as a further gender divide. Girls were offered baby dolls, princesses and sexy fashion figures; the boys section had superheroes, building blocks, science kits and dinosaurs.
"That was it. There was no middle ground. I didn't see any dolls or cooking sets for boys, nor building blocks or fire trucks for girls," writes Atkins Wardy in her new book "Redefining Girly: How Parents Can Fight the Stereotyping and Sexualizing of Girlhood, from Birth to Tween."
After that experience, she said in an interview, "Everything clicked and made sense to me."
"I hear parents saying that all the time. They're like, 'Oh, I just had my sippy cup moment' ... They were at a restaurant and the clown came to the table and offered the boys a whole bunch of selections for what balloon animal to make and then he offered the girl a flower or a tiara," said Atkins Wardy, a mom of two.
"The mom's like, 'What if she wants a light saber, too?'"
The birth of a cause
After Atkins Wardy's eye-opening shopping experience, she decided to start a business creating empowering T-shirts for girls and boys. Her company, Pigtail Pals and Ballcap Buddies, offers selections such as a girl doctor with the headline "Call me in the morning" and another that says "I'm growing up," and lists words like inquisitive, fearless and daring.
Her business led to a blog and ultimately, a cause: trying to raise awareness about gender stereotypes and how damaging they can be.
"One pink pacifier or sippy cup or Lego set isn't a big deal...it's when the lowest common denominators of femininity become the marketing catalyst for every product that's made for females," said Atkins Wardy, who has an 8-year-old daughter and a 5-year-old son.
The fact that there are "girl" products and "boy" products at all is also part of the problem, she said.
"It teaches children there is only one way to be a girl and one way to be a boy," she said. "When you have a little girl like mine who is obsessed with the ocean and giant squids and insect infestations in homes, she's considered weird or odd or a tomboy when in fact, science and things like that should be considered girly."
As a mom of two girls -- including one who hopes Peyton Manning of the Denver Broncos calls her to play on his team in this week's Super Bowl -- I can totally relate. I, along with so many other parents, am frustrated about the definitions of what's girly and what's not, and the separate products and clothing offered to girls and boys.
'Pink and pretty to hot and sexy'
A larger question is just whether this gender differentiation in products and fashion actually leads to another big concern, especially for parents of daughters, the sexualization of our young girls.
Atkins Wardy of Janesville, Wisconsin, says there's a correlation.
"You have to connect the dots," she said. "With princess culture and all these pink toys that are almost always focused on fashion and beauty and how a girl can please somebody else, either by keeping a nice house or looking like a perfect princess, that all segues into the sexualization side of the market.
"Once you're done with princesses, if you are growing up in that girly-girly culture, the next thing offered to you are these sexualized dolls and you are growing up too fast," she said. "You are being introduced into adult concepts of sexuality that otherwise wouldn't be present in toys and it doesn't allow a girl to develop on her own, and at her own pace.
"The pretty princess culture focuses on appearance and that segues (from) 'sweet and pink and pretty' to 'hot and sexy.' There's no room for girlhood in that space."
Encouraging girls' 'personal brand'
So what's a parent to do? Atkins Wardy's book, which she hopes is almost like a "recipe book for parents," offers step-by-step advice.
She encourages us to teach our children to think critically, which can be as simple as watching a television show and raising questions about why girls are portrayed a certain way. For instance, if the girl character is getting rescued by a boy, we can tell our girls the story could easily have been changed so the girl is doing the rescuing.
"I talk about parents teaching girls a personal brand," she said. "She kind of has this benchmark that ... when these toxic messages come in and out from culture, she can then bounce against (them) or not and say, 'Well this doesn't fit what my mom and dad taught me.'"
There are not enough parents having these kinds of conversations with their girls and boys, Atkins Wardy said.
Moms on Facebook might see something inspiring such as a new ad by Dove encouraging women to love themselves, no matter what. "They all click like and they love it," she said, "But are you taking that second step and sharing that with your kid and really talking about it ... and just being conscious of the media you are taking in?"
Parents can also make their voices heard, Atkins Wardy said, whenever they see a product, ad, or clothing that they believe stereotypes and sexualizes girls.
When Disney gave Merida, the heroine from "Brave" a makeover, more than 250,000 people signed a "Keep Merida Brave" online petition. Disney ultimately backed down from changing the character's look and dress.
"Once you aggregate these parents' voices and the tens of thousands of voices, you really can start to make change," she said.
'Once you see it, you can't unsee it'
Atkins Wardy often tells parents in her community that once they become aware of the stereotyping and the sexualization, they won't be able to look away.
"Once you see it, you can't unsee it," she writes.
It's also never too late to start doing something about it, she says. That includes letting our girls know they can be whatever they want to be.
"There are many ways to be a girl and 'Redefining Girly' is about giving girls the space to show us who they are," she said.
So if the Broncos needs an extra player Sunday, I'll be sure my 6-year-old gal is ready!