Platform: Lightning Stylesheets for Visualforce

In the Summer ’18 Release, Lightning Experience Stylesheets are generally available for Visualforce pages. Now, developers can control whether a page is styled with the look of Lightning Experience when viewed in Lightning Experience or the Salesforce app by using the lightningStylesheets attribute. Previously, restyling a page for Lightning Experience involved searching the Salesforce Lightning Design System reference site for matching components. The new lightningStylesheets attribute gives unstyled Visualforce pages the Lightning Experience look, automatically.