The weather's getting warmer and necklines are dipping lower -- sometimes, too low.
From the beach to the mall to the office, women seem to be showing off their cleavage more than ever before. Why? According to Elisabeth Squires, author of "Boobs: A Guide to Your Girls," American breasts are getting bigger while shirts are getting smaller.
"We are seeing more cleavage these days for a few reasons. First, the fashion of the day is tight and skinny. At the same time, women are bigger than they were even 15 years ago. Bra fitters tell me that an E cup is the new C cup," Squires said on "Good Morning America."
"We have to remember that while more women are showing more cleavage, you really have to use your breast power responsibly," Squires said.
What looks sexy for a night out on the town may not be appropriate in the workplace. In fact, Squires said cleavage should never make an appearance in the office.
"It's way too big of a distraction for men and women," she said. "If cleavage isn't in your job description, don't put it in."
But that doesn't mean breasts should stay hidden. According to Squires, the appearance of breasts can help women in the workplace.
"A recent study showed men photos of women in a workplace with large breasts showing cleavage, medium breasts and small breasts. When asked about who looked most professional and personable, the men chose the women with medium-sized breasts," she said.
"You don't have to be flat-chested to be taken seriously," she added. "You just have to be proportionate. For women who are small busted, that may mean a little padding. For well-endowed women, that may mean a minimizer."
Squires suggested that women also keep things respectable at family events, like a kids' soccer game.
"This is not the time to show off your girls," she said. "Your children should not have to compete with your cleavage for attention."
Night is prime time to bring out breasts, but Squires suggested women treat their cleavage as part of their outfit -- not a focal point.
"You can certainly be a bit more daring," she said. "This presumably is adult time, and cleavage is powerful. This is the time to use it. But they should be part of your whole look."
Pregnant women are an exception to the rules. Squires said because pregnancy gives breasts a boost they might not have otherwise, women should show them off.
"During pregnancy you should celebrate your breasts. For some women, that's the only time they have cleavage," she said. "Obviously you don't want to go nuts. But cleavage on a pregnant woman is just different -- live it up a bit."
Squires said women of a certain age can still show off cleavage, as 61-year-old Helen Mirren proved at the Oscars.
"It has to be integrated into your entire look," she said. "If a woman of a certain age squeezes her girls together, she'll get the wrinkled, crepelike look. That's not good. But if you're older and you wear a scoop neck and you have beautiful, what the French call decollete, that's great."
Squires offered advice all women can heed to make their breasts look better:
Don't be in bra denial. The average woman changes bra sizes at least seven times in her life. Get fitted and accept your number and cup size.