For clarification, a molehill is the pile of dirt left above ground when a mole, a rodent a little larger than the average rat, digs its way into the earth. So if you take something small and treat it as if it were big, you are making a mountain out of a molehill. Examples: "I said hello to an old girlfriend last night at the movies, and now my new girlfriend won't talk to me. I say she's making a mountain out of a molehill." "My sister put on a little weight this winter, and now she refuses to be seen in public. She's making a mountain out of a molehill." "Our boss was fired today, so now everyone is concerned that we are all going to lose our jobs. I think people are making a mountain out of a molehill." Note that unless you go into a field like zoology or taxidermy, you will probably never use the word "molehill" except in this particular expression.

A molehill is the same shape as a mountain, just very small in comparison. So if someone reacts to a situation in a MUCH worse way than would be expected, they're, "Making a mountain out of a molehill.". Like, "my boyfriend told me he can't come out with me this Saturday, he said he has too much work to do" - the normal reaction would be, "oh that's a shame, but at least he's getting more money and he will be popular with his boss" - Making a mountain out of a molehill, the reaction would be something like, "HE'S CHEATING ON ME!! I CAN'T BELIEVE IT!! ALL MEN ARE B*STA**DS!!! I KNEW SOMETHING WAS WRONG!! WHY DOES THIS ALWAYS HAPPEN TO ME? I'M GOING TO DIE I CAN'T TAKE IT!!". Reacting to a small issue as though it was a huge issue - and sometimes for the attention. I know someone like that, she, "always makes a drama out of everything".

This is said when someone gets upset about a matter that is not important. They are "blowing it out of proportion". Some men think women do this. A wife might get very upset when a husband does not do something the way she wants him to, and he thinks it's not important. He might say, "why get so upset? You are making a mountain out of a molehill"!

It means something like "You're making something very small (a molehill) into something very big (a mountain)". So it is often said when someone is exaggerating something. But it is also commonly used when someone is very angry or very worried about some very small problem.

I don't see what is hard about this one. Molehill = something very small. Mountain = something very big. Now the molehill won't come to the prophet, so put your thinking cap on, young lady.