In excel how do I keep words from overlapping? ...

I’m making an excel sheet for work, and as I type words into one cell, if they extend longer than that cell they overlap the next cell (assuming that cell is empty, which in this case it is). I’ve made the cells larger (height and width) specifically to make them able to contain all of the words in them, but I don’t remember how to make them drop down to a new line when they run out of space in the cell (ala like word does when you fill a line on a page).

Does anyone remember how to do this? It’s Excel 2003 if it makes any difference. Thanks