According to this theory, time and space are interwoven in a four-dimensional space-time fabric warped by gravitation. It has been verified experimentally recently with the detection of gravitational waves. But the quantum field theory, another leading theory of the 20th century that faithfully describes the world of particles and the infinitely small, would seem to be irreconcilable with general relativity. A universal theory unifying gravitation and quantum physics is therefore the holy grail of physicists in the 21st century. Certain candidate theories predict that the principle of the equivalence between gravitation and acceleration, at the heart of the theory of general relativity, could be violated at very weak levels. Microscope is pushing this principle to its limits and yielding new indications to constrain the theory of general relativity.