How do I start a call from the Messages app?

iOS 12 lets you start audio and video calls directly from the Messages app, how do I do it?

We've all had text message conversations that have turned into too much for texting, requiring a call instead. iOS 12 now lets you easily make that call directly from the conversation rather than leaving and opening your Phone app. Just tap on the picture/name of the person at the top and a menu will appear with options to start an audio or video call, plus an info button for other message thread details.

How to make calls directly from Messages app on iPhone and iPad.