If you want to place a longer text in an Excel cell, it is not a problem if you know that you can enter a newline using the Alt+Enter shortcut key instead of the enter key.
If you write longer texts in a cell more often, you can also automatically fix the line break. Use the Ctrl+1 shortcut key to open the Format Cells window, and then the Align tab. In the Text placement area, select the option Line break into multiple lines. After a click on OK, Excel will accept the change.