Open multiple files simultaneously in vim (all in tabs)

It is surprisingly easy to do. There are several patterns, so it may be useful to learn them all.

Show all files in that directory

vim -p *.*

The -p means open in a tab. You can use wildcards to specify that any file will match. This usage was not possible with tabe. I am looking for another way.

Show all files under that directory

vim -p */*

Show all files and directories under that directory

vim -p *