Google is always been stick to update its popular products. The working culture of Google does match with never say no to innovation. Certainly such attitude gives high dividend. At present Google does little bit changes into Gmail Compose and Reply option. Hoping you are also emulating Gmail for sending or receiving important emails. If you are par with my supposition then you could easily realize changes made by Google otherwise it will be mere acceptance of new changes in Compose and Reply windows of Gmail.
When log in act in Gmail account is made, you would see notification about new changes for try out new compose and reply experience. You may accept and follow given link at the same time. Usually compose option in Gmail takes entire page of your browser but new arrangements lead to open popup windows of Compose email. Here rest of facility for entering email id, subject and putting mailing matter are same like default compose windows.
The new compose features provides facility of Format Text, Attach file, Insert Link, emotions & Photo and other things in same popup window. The compose windows works like Chat window. If you don’t like new compose window and want to come back to default window, click on triangle shaped icon on compose popup window. But in my opinion new Gmail is more valuable in terms of sending or receiving emails more quickly. It will be more useful for those, who have to handle lots of emails each day.