There is a popular idiom that native English speakers use to ask someone else to tell them the whole story. Usually this idiom is used in a more friendly or informal way...
If we are in a conversation with friends, and are asking someone to tell us the whole story we would use the idiom "spill the beans"
For example, if a friend has something interesting to say or is perhaps only telling you a little of a story, we would say "come on, spill the beans.." asking them to tell us the full story..
A friend may come up to you and say something such as:
"Hey, I met the actor George Clooney yesterday"
"Really? Wow, where did you meet him? come on, spill the beans!"