How do they get young children and infants to cry on cue in TV shows and movies?!

How do they get young children and infants to cry on cue in TV shows and movies?

An older child could be taught to cry when they need to. But what about a very young one. How do they get them to cry when they need them to? I have seen tv shows and movies when the camera is looking at the child who is not crying, and then suddenly they start to cry. I remember hearing when I was a kid that someone would poke them with a pin or something to make them cry. I would think and hope this would not be allowed.

5 days ago
I know what editing is, I was just wondering how the got them to cry to in the first place.

Infants cry whenever they feel the need to. Small kids when needed to cry usually have to watch a parent or parents leave the room while filming just to get them to cry during a scene. I seen on television once how a child actor would be happy one minute in front of the camera then turn around and cry all of a sudden, they use the real parent as a focus point. Once that parent or parents are gone for a quick second the child start crying automatically.

(That is the only thing I can think of)