I do not understand and cannot comprehend anything existing in a single dimension. I have heard briefly that strings exist in a single dimension. How would you describe a single dimension? I understand 3 dimensions, length- height-depth. But wouldn't a single dimension object be invisible in two dimensions? Also, if it were a single dimensional object, how would it exist? I mean, if it were composed of "something" wouldn't it have to be more than one dimension? Any explanations would be appreciated.