Remember the Boos from the Super Mario series? They move towards you when you're not watching, but the second you turn, they freeze in shame. In a similar, but opposite way, scientists have found that unstable uranium stops decaying when they observe it!
After a day of looking at some unstable uranium, scientists in Texas noted that the uranium would decay when they weren't looking, and stop the decay when they did look at it. It was as if the element knew when it was being observed. They thought it might be a fluke, but the results were the next day. They reported it to other labs, who corroborated their story!