It is generally accepted that our observational knowledge in cosmology is severely restricted, not only as a practical, contingent state of affairs, but in principle as well. We can only see a small fraction of the universe, so to verify our cosmological models we have to assume that our perspective upon the universe is highly typical.
I've just written a new paper which seeks to demonstrate that, on the contrary, it is possible, in principle, to obtain knowledge of the entire universe at the present time, even if the radius of the universe is much larger than the radius of the observable universe. I achieve this by proposing that outer space is joined to inner space, in the sense that each elementary particle contains the universe to which the elementary particle itself belongs.
In such a space-time, each elementary particle is simply an embedding of the universe within itself. If one tries to probe the inside of an elementary particle, then one is probing inside the entire universe, for the boundary of the elementary particle is also the outer-most boundary of large-scale space-time. In such a universe, one really can see the universe in a grain of sand.