Microsoft has released the Azure Active Directory Connect to the general public. Azure AD Connect replaces (although "incorporates" is a better word) DirSync as the new tool to set up synchronization between your on-premise Active Directory and Azure Active Directory, including Office 365.

The current version of Azure AD Connect is only the beginning. Microsoft has announced a lot more features, which will be made available in the next versions.

More information and installation resources: https://azure.microsoft.com/nl-nl/documentation/articles/active-directory-aadconnect/