What is the smallest particle of matter known?
So far it looks like there is nothing smaller inside an atom than quarks. Experiments look for evidence that quarks have some sort of shape or structure. If they do have a shape or structure rather than just being a point (which by itself is a very difficult concept to understand), then there might be some sub-quark constituents. At present there is little or no evidence of any structure to the quark.
What is the biggest thing in our universe?
(The fabric of the universe itself is estimated to be 150 billion light years across - galaxy clusters stretch billions of light years across the cosmos )
According to the standard model of galaxy formation, the biggest galaxies are elliptical monsters formed from the collision of many smaller galaxies. The largest known example is the lens-shaped IC 1101, a billion light years away in the centre of the Abell 2029 galaxy cluster. IC 1101 is close to 6 million light years across, making it thousands of times the volume of the Milky Way.
The biggest hole.
Not a black hole, for a change, but a vaster expanse of darkness. On the largest scales explored, galaxies are arranged into great walls and knots as much as a few hundred million light years across, with voids in between. The biggest known void - freakishly large at around a billion light years - was found in 2007. One outlandish suggestion is that it is a blemish left by an ancient close encounter with another universe.
The Biggest Star.
A star called VY Canis Majoris, 5000 light years from Earth could swallow our sun 8 billion times over. Probably. Its estimated diameter of nearly 3 billion kilometres puts VY Canis Majoris in with a handful of stars that have earned the title red hypergiant. This estimate is contested, however, and some say the star is a mere red supergiant only 1 billion kilometres across.