Defining tables in Asciidoctor is very easy. The start and end of the table are defined by |===. But if we want to add a new table to a table cell we cannot use the same syntax. To define a nested table we must replace the | separator with !. So instead of |=== to indicate the table boundaries we use !===. Also the cell separators are now ! instead of |. Finally we must make sure the table cell or column supports Asciidoc markup, so the table is properly created. We must configure the cell or column with a so the nested table is created.

In the following example Asciidoctor markup we have a simple table with a nested table in the second column and row. Notice we can still apply all table configuration to the nested table as well: