With Iterations you can save different phases of your prototype as separate versions and use them to evaluate design ideas. You can also share preview links to past iterations to collect feedback — all this without the need to share your work while it's still in progress.
All iterations of a given prototype are in the Iterations modal. You can open it from Top bar in the Editor or from the dashboard — hover over the prototype and open more options. You can then edit, preview retrieve or remove iterations as well as create new ones.
Open the Iterations modal in the Top bar and choose Create new iteration, name your file and decide if you want to copy comments from the prototype. It's best to use descriptive names for your iterations to keep your file structure neat. In the Iterations modal, you can also edit existing iterations, create new iterations out of existing ones, retrieve and delete them.
If you retrieve an iteration, it’ll become the current version of the prototype. The previous version will be automatically saved as a new iteration in the history — you’ll be able to access it anytime.