Besides changing the font, after you've selected text, there are other ways to change it quickly and dramatically.
On the Formatting toolbar, clicking the capital A with the up arrow increases the font size and the down arrow makes it smaller.
You can also accomplish the same task by pressing the Ctrl and Shift keys and pressing the > key for enlarging text and pressing the < key for making it smaller.
To change the case of text to all capital letters, select the text and press Shift+F3. Pressing Shift+F3 on all capitals changes the selected text to lowercase.
If you want subscript or superscript text as shown here
Hello World Hello World
select the word to be changed and press Ctrl+= (equal sign) for subscript and Ctrl+Shift+= for superscript.