Microsoft is working on adding the Gmail support to their Outlook.com service, that will allow you to use some Gmail features directly on Outlook. You'll be able to access Google Drive files in order to attach them to emails, and see Calendar.
Outlook.com is Microsoft's very own email and calendar service which requires a Microsoft Account to access its features. It has very tight integration with Windows 10, OneDrive, Microsoft Office, and other company's products.
The new option is a work-in-progress, and is not available widely yet. As of now, it supports only one Gmail account.
Image credits: Florian B
The key change here is the ability to access your Gmail data via the web version of Outlook. Microsoft's Desktop apps, such as Calendar and Mail in Windows 10, already include support for this feature, allowing you to access e-mail and calendars from Google. Additionally, the GDrive integration is also a new feature, and it looks promising.
As of now, it is not known when Microsoft will release the update to the public.
Thanks to Neowin.