Adding Preheader text in Marketo Editor

It would be useful to update the email editor by adding a preheader text for a mailer content.

We have tried for once in the HTML editor using the HTML scripts, but when we saw the test in gmail, the Preheader text shown in the mail as the first line.

We need to use the Preheader text for our mailer to reveal the short content to describe the mailer reason other than the Subject.