Draw some diagrams of objects in physics, marking some areas "Here be dragons", signifying the unknown.
Some region very close to the center of an electron: We've verified electrons behave like a point particles only to a certain scale. Smaller than that, we don't know their structure.
Some region close to the center (hypothetical singularity) of a black hole: We don't have a good theory -- quantum gravity -- of matter at extremely high densities at very small scales.
Timeline of the very early universe.
All are "beyond the Standard Model".
Others? Probably many. Core of Jupiter, deep internal structure of neutron stars.
EmoticonEmoticon