• MakeBoxes[expr, form] is the low-level function used in Mathematica sessions to convert expressions into boxes.
• MakeBoxes does not evaluate expr.
• You can give definitions for MakeBoxes[expr, form] to specify your own rules for how expressions should be converted to boxes.
• MakeBoxes is not automatically called on the results it generates. This means that explicit MakeBoxes calls must typically be inserted into definitions that are given.
• If you change the output format for an expression by giving a definition for MakeBoxes, there is no guarantee that output you get will subsequently be able to be interpreted by Mathematica.
• Definitions you give for MakeBoxes will override built-in Mathematica rules for generating output.
• New in Version 3.