Lightning Experience: A New, Modern, Intelligent User Experience

It’s here ... the new Salesforce user experience! Lightning Experience is a completely reimagined interface. Even better, it’s built on our UI platform, so the experience can grow and evolve with your needs. Learn about the benefits of this intuitive, efficient interface. Then decide when it’s time to make the switch—the power is in your hands. (If you used person accounts in your production org before now, Lightning Experience is available within 24 hours after the Spring ’16 release. Otherwise there’s no wait.)
Available in: Group, Professional, Enterprise, Performance, Unlimited, and Developer Editions