Grouping related graphs or images into a single figure (a panel) is strongly encouraged. When a block of illustrative material consists of multiple parts, each part should be labeled with sequential uppercase letters in the order of their citation in the text (A, B, C, etc.). The letters identifying individual images should be placed within white circles in the lower right corner. To separate grouped images, authors should insert white frames (1mm thick). Individual images (not grouped into panels) should be identified with sequential Arabic numerals in the order of their citation in the text (Figure 1, Figure 2, Figure 3, etc.), presented in the same manner, with letters identifying individual images, as described for panels above. The number identifying a grouped figure (e.g., Figure 2) should not be inserted into the panel but referenced only in the figure caption and text (e.g., Figure 2A-C). Scale bars, when necessary, should be positioned in the lower right corner of the figure. The units of the scale bar should be provided at the end of the figure caption or, when a figure contains multiple scale bars with different units, above each bar. Details within a figure can be indicated with arrows, letters, or symbols, as appropriate.