How Visual Cues Can Help Tell the Story

Scientific figures are, by and large, not evaluated as works of art. Yet employing artistic approaches and principles when designing and creating figures can help improve their effectiveness. After all, both art and scientific figures, at their core, are the combining of visual elements together in a manner to convey an intended message. As such, scientists should give greater consideration to what elements they choose to place within their figures and what message they are trying to send to the audience through those elements. 

Transitioning to Color

In the past, scientific manuscripts were for the most part monochromatic. Applying color was a difficult and labor-intensive process, both during design and composition as well as publication. As a result, scientists created new methods for distinguishing visual elements, such as using different grayscale shades or employing hatching or stippling to create distinct patterns. But there are limits to what one can do when restricted to only shades of gray. Modern research, with its experiments capable of probing thousands of data points simultaneously, needs more ways to differentiate between measured variables. 

         

This is where color comes in. Whereas an 8-bit grayscale image offers 256 shades from white to black, an 8-bit red-green-blue (RGB) image offers 256³—or 16,777,216—options, giving scientists more flexibility than they are likely ever to need. Adding color also lets scientists visually link data together, such as multiple members of the same signaling pathway, or set them apart, such as putting a particularly striking finding in a vibrant color among a sea of darker hues. Maintaining color consistency also lets scientists tether multiple panels or figures together. Using the same color for the same experimental group throughout the manuscript allows the audience to quickly and effectively recognize what they are looking at.

This digital age has largely removed the barriers to using color. Today, adding and changing color to a scientific figure can be done with a few clicks of a mouse. Similarly, most of the audience will be viewing the manuscript on a digital platform rather than manually printing black-and-white hard copies. As such, researchers no longer need to be overly concerned with maximizing contrast in consideration for how a figure will look in grayscale.

Nonetheless, color can be a double-edged sword in terms of both aesthetics and accessibility for readers with color blindness. Designers can get carried away, making color choices and creating combinations just because they have the capability. Color selection should be reasonable, adhering relatively closely to primary, secondary, tertiary, and quaternary hues. Color combinations should be made in accordance with the desired message—similar shades for associated objects, contrasting hues otherwise, and neutral black, white, or grays for control groups. Finally, color decisions should be made to fit alongside white empty space and black lines (e.g. for axes, text, or borders).

Applying Visual Elements to the Message

Colors are useful for creating effective figures because they set design elements apart. However, they have limited power if the elements themselves are not present or used inappropriately. For scientific figures, design elements include things such as arrows and boxes meant to guide the audience from one part to the other. They also include schematics, representative imagery, and in-set images that highlight or zoom in on key aspects of a more complex diagram. 

For example, Kang Wang and colleagues at Purdue University used a schematic figure at the beginning of their Nature publication¹ to summarize a core concept of their study: the relationship between intermolecular distance, potential energy, and molecular emission. Moreover, they also provided inset diagrams showing how molecules would be physically arranged in these scenarios, from aggregation to single molecules in solution. 

This figure also has two other key aspects. First, red is applied to visually group elements pertaining to single-molecule-like aggregates, indicating that SMAs will be a topic of discussion moving forward in the manuscript. Second, the consistent application of a green color to the molecules further creates a visual association with FITC, arguably the most commonly used fluorophore, to better emphasize the objective of this study: to better understand photoluminescence.

In another example, Lukas Kremer and colleagues at the German Cancer Research Center in Heidelberg² similarly used the first three panels of their first figure to provide a schematic of an experimental protocol. However, rather than just using labels and text boxes to create a rather dry flowchart, the authors employed iconography to guide their audience through the single-cell sequencing process. They also provided an anatomical diagram to show the brain region that they sampled for this sequencing—the ventricular-subventricular zone—while at the same time explaining the neural stem cell lineage that they examined. Moreover, the diagrammed schematic of this lineage was color-coded to match the representative transcriptomic and epigenomic data shown in panel c (something that comes up again, with excellent effect, in Figure 4). All in all, the authors provided a visual progression from organ to cell to gene, while explaining how these links guided their study design. 

Striking a Balance between More and Less

In the end, the purpose to everything in a figure, from the color selection and the elements and visual aids to the data itself is to make things clearer for the audience. As such, the main question for scientists when designing figures is simple: “Does my decision help my message?” If the answer is no, then the designer must have the awareness to take a step back and recognize that what they have done may have made the study more difficult to understand. Sometimes, taking something out can be just as useful as putting something in.

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