Making beautiful, professional looking reports in Cosmos is easy thanks to the fact that Cosmos is built within Excel and Excel Online. Formatting is all controlled through the familiar Excel interface so users can quickly format text size, add images and logos, and have full control over the final output of the report.
To apply formatting to a report, the user will select the cell, or range of cells, to be formatted and then leverage the built-in Excel formatting tools to apply the desired formatting. The user has full control over font sizes and colors, images and logos, cell shading, and the use of built-in Excel styles.
Microsoft has guidance on general formatting tips and principles here: Ways to Format a Worksheet.