Nightmares - we all have them. They are essentially nasty dreams that trigger emotional responses from our minds, such as fear, horror, despair, anxiety and sadness. Whether they involve minor inconveniences or truly terrifying scenarios, not all dreams are sweetness and light. Although nobody truly knows what causes the phenomena of nightmares as we sleep, theories include real life stress, breathing problems and even supernatural causes but, regardless of the cause, the effects aren't very nice. They put us in to situations that we'd rather not be in and, whether it be situations of danger, discomfort or psychological or physical terror, we can often wake up terrified (and, ultimately, relieved) having experienced things in our sleep that we'd prefer to avoid experiencing whilst awake. One of the most amazing things about nightmares is that we all tend to experience the same ones. When you think about it, it truly is a remarkable thing that this occurs because, of the millions of things we could have nightmares about, everyone tends to share a small recurring number of similar or identical nightmares. In this article, we're going to take a look at several nightmares - ones we all seem to have experienced at some point or other - and what they are said to mean. Here are ten common nightmares that everyone seems to have...