PointSize
[t] PointSize
can be used for both two- and three-dimensional graphics. The initial default pointsize is 0.008 for two-dimensional graphics and 0.01 for three-dimensional graphics.
Table[Graphics[{PointSize[r], Point[{0, 0}]}], {r, {0.02, 0.05, 0.1, 0.3}}]
Table[Graphics3D[{PointSize[r], Point[{0, 0, 0}]}], {r, {0.05, 0.1, 0.8}}]