Any standard shape can be converted into a table by inserting some rows and columns using the Table tab. First, select the shape, then click the Table tab and specify the number of rows and columns, and finally click on Insert Table. This inserts the desired table into the shape or shapes currently selected. Any text inside the shapes is placed in the first cell of the table.
Non-rectangular shapes may also contain tables:
Depending on how many rows or columns you selected, your shape may grow to accommodate the inserted table.