What is the nature of space time at 1 picometer?

Answer 1

It is a measure in 1 dimensional space. No time dimension.

Answer 2

At a scale of 1 picometer, which is one trillionth of a meter, the nature of spacetime is still governed by the principles of general relativity, but quantum effects become significant. At such small distances, the concept of continuous spacetime breaks down, and a quantum theory of gravity is necessary to fully describe the nature of spacetime.