Can you turn on APU in flight?

Excuse me, I was wondering if you could shed some light on a technical matter regarding aircraft systems. Specifically, I'm curious about the possibility of activating the Auxiliary Power Unit, or APU, while the plane is already in flight. Is it a standard procedure or a capability that exists in modern aircraft? I understand safety protocols are paramount, so I'm eager to learn if such an action is feasible under any circumstances and if so, what the reasons or benefits might be. Thank you for your time and expertise on this matter.