In "Ant-Man," the hero shrinks down to the size of an insect thanks to "Pym particles." Rick Moranis uses a shrink ray in "Honey, I Shrunk the Kids." Even back in 1865, when "Alice's Adventures in Wonderland" was published, the public was enthralled by the idea of entering a miniaturized world of wonders.
So what's the hold-up? Why haven't scientists given us shrinking technology already? Because it's impossible for many, many reasons.
"Shrinking would mean one of two things," Erik Aver, an assistant professor of physics at Gonzaga University, told NBC News. "Your atoms would either have to shrink or you would have to be made out of less atoms."
Atoms don't shrink. The average distance between the protons and neutrons that make up the nucleus of an atom and their surrounding electrons can't be changed.
Even if somehow a mad scientist could shrink all of the atoms in someone's body and bring her to the size of an ant, that person would become so dense that she might sink through the Earth.
The other option is removing atoms. That could theoretically work ... up to a point. There is a minimum number of atoms that make up a cell wall or strand of DNA.
Related: Who is Ant-Man? 5 Little-Known Facts About Summer's Smallest Superhero
"You can't build a castle out of four Legos," Aver explained. "If you had a castle made out of a million Legos, you might be able to shrink it down to something that looks the same with 1,000 Legos, but there is a limit."
So transforming Paul Rudd -- who stars in "Ant-Man," which opens Friday -- from 5' 10" to 5' 2" might be possible, but not down to the size of an insect.
There is another problem: biological systems don't always scale up or down. The amount of oxygen we take from the air, the food we digest, the heat we give off; these all depend on the surface area of our organs and the mass of our bodies.
"It's not as simple as saying, 'Oh, everything will shrink down and stay proportional,'" Michel Boudrias, biomechanics expert and chair of the environmental and ocean sciences department at the University of San Diego, told NBC News.
You can't just make organs smaller without consequences. Take the lungs, for example. Shrink them length-wise by a factor of two, and the surface area decreases by a factor of four and volume by a factor of eight. That drastically affects the rate of diffusion of oxygen and carbon dioxide in the lungs
In a highly entertaining paper called "The Biology of B-Movie Monsters," Michael LaBarbera, professor of organismal biology and anatomy at the University of Chicago, explains how shrinking down a man by a factor of 70 would reduce his surface area -- through which the human body sheds heat -- by a factor of 5,000 times. His mass, which generates his body heat, would be reduced by a factor of 350,000 times.
That would mean he would need to boost his metabolic rate. "Like a shrew," wrote LaBarbera, "he'll probably have to eat his own weight daily just to stay alive."
It's hard to fight crime when you're eating 24 hours a day. Moving around might be difficult, too. Remove muscle strands to reduce Ant-Man's mass and he would become weak. Shrink down the atoms to keep the same muscle structure and Ant-Man's incredible density would muck things up.
In the comics, Hank Pym solves this problem by discovering some physics-defying, subatomic Pym particles. Impossible? Sure. But at least it sounds more fun than getting bit by a radioactive spider.
