What is wrong here -- >> name = "Tito" >> str1 = "Treehouse loves {}" >> subject = str1.format(name)

There is nothing inherently wrong with your code. But the challenge checker for these tasks can be pretty picky. Even if the result is correct if you did not achieve the result in the way that is expected your code will often be marked as wrong.

The problem in this specific instance is that you create the str1 variable and assign the message to it, you can complete this challenge without doing that. You can simply use format directly on the string as you assign it to the subject variable like this:

name = "Tito"
subject = "Treehouse loves {}".format(name)

That is the way the challenge checker expects you to solve the problem, and as such is the only solution it will accept.