# data[].attributes.attachment_link.readable_text
Not too long ago, most Americans associated tattoos with sailors, bikers and sideshow artists. But tattoos have become more popular in recent years, and the people who get them are as diverse as the styles and designs they choose. And some people who would never think of tattooing pictures or symbols onto their bodies use permanent makeup -- a type of tattoo -- to emphasize their eyes and lips.

In this article, we'll look at how the tattoo process works and examine the safety and legal issues surrounding it.

Artists create tattoos by injecting ink into a person's skin. To do this, they use an electrically powered tattoo machine that resembles (and sounds like) a dental drill. The machine moves a solid needle up and down to puncture the skin between 50 and 3,000 times per minute. The needle penetrates the skin by about a millimeter and deposits a drop of insoluble ink into the skin with each puncture.

The tattoo machine has remained relatively unchanged since its invention by Samuel O'Reilly in the late 1800s. O'Reilly based his design on the autographic printer, an engraving machine invented by Thomas Edison. Edison created the printer to engrave hard surfaces. O'Reilly modified Edison's machine by changing the tube system and modifying its rotary-driven electromagnetic oscillating unit to enable the machine to drive the needle.

Modern tattoo machines have several basic components:

A sterilized needle

A tube system, which draws the ink through the machine

A foot pedal, like those used on sewing machines, which controls the vertical movement of the needle.

When you look at a person's tattoo, you're seeing the ink through the epidermis, or the outer layer of skin. The ink is actually in the dermis, which is the second layer of the skin. The cells of the dermis are far more stable than the cells of the epidermis, so the tattoo's ink will stay in place, with minor fading and dispersion, for a person's entire life.

Next, we'll look at how artists actually create tattoos, from preparation to finishing touches.

# data[].attributes.attachment_link.description
Not too long ago, most Americans associated tattoos with sailors, bikers and sideshow artists. But tattoos have become more popular in recent years, and the people who get them are as diverse as the styles and designs they choose.

# data[].attributes.attachment_link.readable_text
Above, you can see the latest video in the American Chemical Society's Reactions series. You can also see me (yes, me) getting a tattoo! For science! And no, it's got nothing to do with Pittsburgh, random men who keep emailing me about Pittsburgh. It's the astronomical symbol for Pluto, with an added "CH" for its largest moon, Charon.

My new tattoo is reeeeeally esoteric and not right side up but use your context clues pic.twitter.com/U0qjoV1aL0

- Rachel Feltman (@RachelFeltman) July 2, 2015

I'm thrilled to have finally been given an opportunity to show off my unique talent for reciting scientific information from memory while getting stabbed with tiny needles over and over again.

[Interactive: Thinking of inking?]

If you're hungry for more tattoo science -- or just on the fence about getting inked -- here are some good factoids to know:
Tattoos might make you feel good
Really! There are the obvious chemical responses, for starters: You're going to have a rush of adrenaline, because someone is coming at you with a needle. And you're going to get some pretty nice endorphins, too -- your body's chemical response to pain -- which can make you sort of high.

But there's more too it than that. According to one (admittedly small) study, a new tattoo might improve your self-image for weeks after the fact. And why not? You've got art on you!

Ready for #Pluto

A photo posted by Rachel Feltman (@rafeltman) on

The effect might even be long-term for men, though most women in the study got anxious a few weeks in -- possibly because they started worrying about how other people saw their tattoos.
Some tattoos might even be medicinal
There's evidence that tattoos found on ancient humans may have been deliberately placed over acupuncture points to provide a more permanent therapeutic effect. Even today, some cultures practice medicinal tattooing to cure certain ailments, with the most convincing effects seen in arthritic joints.

[At D.C. Tattoo Expo, judges pick the best designs - and see at least one of the worst]
Tattoo needles don't work the way you think they do
Lots of people seem to think that tattoo needles shoot ink into your skin. That's an understandable misconception, because most "needles" we're exposed to are used to inject things.

But that's not how tattooing works.

It's actually all about capillary action. The ink is held between separate itty bitty needles -- the same way ink is held between strands of hair on a paintbrush -- and when those needles puncture the skin, the ink is sucked down into your skin. Physics!

If you're having trouble visualizing how that works, you can check out a slow-mo tattoo gun in this previous post, which features an amazing tattoo video from Smarter Every Day.
Tattoos become permanent by hijacking your immune system
Tattoos: Not just a rebellion against mom and dad. You're pretty much duping your entire body when you get inked.

Here's how it goes. When a tattoo needle punctures your skin, your body does what it does whenever anything punctures your skin (duh) and tries to close the holes up. The cells that rush to the rescue arrive to find not just a wound, but also a foreign invader -- the ink.

The indignity!

Those cells gobble up the ink, but some of them get stuck in the dermis layer of your skin. When you look at a tattoo, you're not just seeing little bits of ink trapped under your skin. You're actually seeing ink trapped inside cells that had hoped to destroy that ink. Those odd bedfellows stay visible pretty much forever, fading and laser removal (which works by busting the ink into smaller particles that can be carried away) notwithstanding.

Typical level of coordination.

A photo posted by Rachel Feltman (@rafeltman) on

Tattoo ink is a cornucopia of different chemicals
Every tattoo ink is different -- if you get two tattoos in the exact same shade, but get them at different times and from different artists, the chemical compositions probably won't match.

And a lot of artists don't mix their own inks, but buy them from companies that hold on tight to their formulas, meaning that the person putting ink in you might not know what's in it. So if you have allergies -- especially to heavy metals, which provide the color for a lot of known ink formulas -- take extra precautions.

One survey of New Yorkers found that 10 percent had skin problems after getting a tattoo. When you consider that tattoo ink is basically a mystery, those odds don't seem so bad. And some of those incidents were no doubt due to improper aftercare. It's important to remember that your tattoo is an open wound just like any other (at least until it heals) so follow your artist's instructions!

Some have even suggested that tattoo inks might be carcinogenic. Because they're unregulated and vary so much, it's hard to gauge how much of a real risk this might be.
Tattoos hurt, but ¯\_(ツ)_/¯
As someone with several tattoos, including one in a notoriously painful spot --

This was sensible

A photo posted by Rachel Feltman (@rafeltman) on

-- I get a lot of people asking me where they can get tattooed and have it hurt the least. Bad news, guys: No scientific study to back this one up, but just take my word for it -- everyone is different. You can check out this chart to see which body parts are general ouch zones (top of the foot, never again) but the pain of tattooing is just like any other pain -- it's highly subjective.

I and many others will say that it's the bony areas that hurt the most, but some folks will swear it's the fleshier parts of their body where they were really unbearable. Sometimes a tattoo gun will go right over a particularly sensitive nerve. Some people have a better experience when they can see the needle in action (and freak out if they can't) and others prefer blissful ignorance of its machinations.

You won't know until you try. And then you'll get your second tattoo somewhere else and cry like a baby because you weren't expecting it to hurt so much more than the first one did. It's all good.
There are some downsides
There are things you can't do with a tattoo. Laser hair removal, for one. Because the process works by targeting dark pigment, tattoos will end up drawing the laser's ire and get blistered and burned.

If you've got a colored tattoo, chances are pretty good that the metal content of the ink will be enough to make MRIs...interesting. The effect of metal inside a tattoo can range from a weird tingling feeling to a painful burn, but neither are any reason to avoid necessary diagnostic imaging -- just be prepared.

And tattoos can even interfere with your ability to adopt new technologies. Apple recently admitted that some users of the brand's smartwatch wound up disappointed when their wrist tattoos interfered with the device's sensors.

So if you're considering some body art, keep in mind that there's more to a tattoo than just the look of it. That ink might be a pain in the butt one day, so you had better make sure you love it.
Read More: Watching a tattoo needle in slow motion reveals the physics of getting inked "My favorite tattoo is in my armpit" and more stories behind the ink The chemistry that makes your wine taste good (or bad) Science finally tells us how cats want to be petted The science behind perfect grilling

# data[].attributes.attachment_link.title
All the science that goes into a single tattoo

# data[].attributes.attachment_link.description
Above, you can see the latest video in the American Chemical Society's Reactions series. You can also see me (yes, me) getting a tattoo! For science! And no, it's got nothing to do with Pittsburgh, random men who keep emailing me about Pittsburgh.