Atomic scientists moved their "Doomsday Clock" closer to midnight than ever before, citing Russian nuclear threats amid its invasion of Ukraine and other factors underlying the risks of global catastrophe.

The Bulletin of Atomic Scientists announced Tuesday that the "Doomsday Clock" is now set to 89 seconds to midnight.

The Doomsday Clock now stands at 89 seconds to midnight, the closest to catastrophe in its nearly eight-decade history. Here's a look at how — and why — it's moved.