Figures are an important component of any manuscript; they are perhaps the most impactful means of communicating your story. However, journals understandably impose restrictions on figure count. Further, telling the complete story using the least number of figures increases readability and clarity.
One approach to integrating figures and reducing the total number is the use of multiple panels within a single figure. There are a few helpful points to keep in mind:
1. Panel content that would benefit from being juxtaposed. Changes in one variable relative to another are best included within the same figure.
2. Try to panel content that share axes, units, legends, etc. It will make a densely paneled figure more intuitive to view for the reader.
3. Identify each panel in some way (e.g., letters, lower case Roman numerals) as you need to be able to refer to each panel in the manuscript text.
4. Ensure that there is appropriate spacing and layout to clearly separate each panel. Ambiguous overlap or bunching of material closely together makes it difficult for the reader to process the figure.
5. If using color, ensure that the color scheme is consistent across panels. Again, this will ease viewing for the reader.
6. If possible arrange the panels in such a way that the least complex is viewed first and the most complex last (panels will typically be read left to right, top to bottom. This is particularly apt when the panels represent different experimental groups or conditions.