Change required site registration information (end user side)

What is the minimum information required to set up a site for an end user?

By default, WP asks an users to Username, Email address, Site name, and Site title. Then the password is given via email.

I want my user to put as little information as possible to create a site. For example entering ID/PW will create a site for them. Simplifying the registration process.

Your help will be much appropriated!

Thanks in advance.