This is an email subscription form designed by Ahmad Shadeed where you accept the user’s email address as the input. It starts off with a button that you can use as a Call To Action element on your landing page and when you click on it, it morphs to a text field where you can enter an email address and a submit button.
If you are having trouble with the pen, try the archived copy on GitHub
Button Morph to Email Input Snippet
See the Pen Subscribe Form #1 by Ahmad Shadeed (@shadeed) on CodePen.0