(DISCLAIMER: All of this is only from what I know; please correct as necessary.)
I have come up with a very cogent theory for the origin of matter in the third dimensional plane. If you recall Einstein's explanation of gravity (space is a flat plane, and any object with mass creates in indentation upon it;
like placing a rock then a marble on a piece of fabric drawn taut, the marble will roll towards the rock because it indents the fabric), I think it possible to have an object so massive that it rips through this fabric breaching into a lower or higher dimension.
So, imagine having this happen fourth-dimensionally; there is an extra dimension and different physical laws, so, an object could be much more massive (assuming gravity exists fourth-dimensionally.
So, Imagine this object tearing through the fabric of the fourth-dimensional plane, and breaching the third dimension; with one less dimension, gravity would act less upon this object, possibly causing a massive explosion (think Big Bang

), and introducing a large amount of matter into this empty third-dimensional plane.
Please tell me what you think of this theory.