Microsoft's Halo series, one of the company's crown jewels, has reached a new sales milestone. The sci-fi shooter series, which debuted in 2001 on Xbox with Halo: Combat Evolved, has now sold more than 65 million units, Microsoft announced.

This is up from 60 million Halo titles sold worldwide in October 2014.

Helping to push Halo to its new sales milestone was in all likelihood November 2014's Halo: The Master Chief Collection. Microsoft has not announced a specific sales figure for this game, but it's likely that it continues to move units, as it's now featured in Xbox One system bundles.

The Halo series continues this October with Halo 5: Guardians. Looking beyond that, Xbox boss Bonnie Ross recently said that there are still "hundreds" of stories from the Halo universe to be told.

For a closer look at Halo 5, including its Warzone mode, check out the video above.

At Comic-Con last week, developer 343 Industries responded to concerns about the fact that the $250 Halo 5 Limited Collector's Edition does not come with a physical disc. The developer also warned fans not to rush through the game's campaign and discussed Halo 5's length and 60fps frame rate.