Even with all that research, there’s some room for artistic licence. Illustrators follow some conventions about color based on what’s generally true in nature—veins are always blue, for instance, and arteries are always shown as red. But the microscopic structures inside cells are smaller than the wavelengths that create visible light, so they don’t have their own color. As a result, no standard color code for them exists. “The great thing about molecules is they’re too small to have color, so I get to pick anything,” Falconieri says.
Falconieri does her best to be as accurate as possible but, she says, “‘accurate’ is a moving target.” After she finished her illustration of SARS-CoV-2 for Scientific American in mid-May, for example, researchers uncovered more details about the virus. “If I were to do the illustration again, it would reflect new science, like the flexibility of the spike protein’s stem, and the organization of the RNA and protein inside the virus,” she says. “That’s the great thing about medical and scientific illustration: Because science is never done, my job is never done.”
Oftentimes, illustrators will have to decide when to sacrifice accuracy in favor of creating an image that explains a concept more clearly. “If a researcher is talking about this particular place in a protein as a binding site, of course we’re going to be accurate,” says Alan Hoofring, lead medical illustrator at the National Institutes of Health Office of Research Services. But if the illustration is meant to emphasize something other than that specific site, Hoofring might simplify that part of the image, substituting a general shape for the protein and the binding location, rather than trying to replicate them in intricate detail. That’s because other parts of the information design might be more important.
As another example, if an illustrator is trying to show how SARS-CoV-2 binds to a lung cell, enters it, and starts reproducing, it’s important to make sure viewers can follow that process clearly. In this case, top priority goes to making the chronology clear. “Medical illustration is just all about putting arrows in the right spot,” Hoofring jokes.
And how much information gets included in each image depends a lot on who the image is for. For example, an image of DNA that doesn’t show the correct number of base pairs might not be exactly accurate, but it might be enough to get an idea across to a viewer who isn’t an expert in genetics. “It’s a judgement call,” says Joanne Muller, president of the Association of Medical Illustrators. “You don’t want anything to be untruthful. It has to be correct. But you don’t necessarily have to tell them everything about everything, because that’s confusing.”
That’s not the same as making mistakes, and a few common errors are huge pet peeves among illustrators. Sometimes brains are drawn backwards, with the brainstem and frontal lobe facing the wrong way, or knee and elbow joints are depicted bending in the wrong direction. There are the bladders shown as being half full, even though the bladder doesn’t actually hold any air. (It just expands as it collects more urine.) And there’s the industry’s number one complaint: DNA that twists left instead of right. “Backwards DNA always gets me,” says Falconieri.
Those details may seem small, but as more and more scientific topics like Crispr, vaccines, and Covid-19 emerge in pop culture and politics, it’s increasingly important that the public has access to accurate information that they can understand. “It’s a really interesting time to be involved in science illustration, because more complex science is becoming more relevant in everyday life,” says Maya Kostman, who makes illustrations for the Innovative Genomics Institute at the University of California, Berkeley. For example, she says, take the Covid-19 vaccine. People want to understand how it was created, researched, and tested. But just making a report from the Food and Drug Administration public might not be enough to answer peoples’ questions. “How is someone going to interpret that? It’s very hard and it’s becoming more and more important for it to be an understandable concept,” she says.