Choose this command to show previously hidden rows or columns.
To show a column or row, select the range of rows or columns containing the hidden elements, then choose Format - Rows - Show or Format - Columns - Show.
For example, to show the column B, click on the header of the column A, expand the selection to the column C, then chose Format - Columns - Show. To show the column A previously hidden, click on the header of the column B, keep the mouse button pressed and drag on the left. The selected range displayed in the name area changes from B1:B1048576 to A1:B1048576. Choose Format - Columns - Show. Proceed the same way with rows.
To show all hidden cells, first click in the field in the upper left corner. This selects all cells of the table.