Very light scalar fields could be at the origin of large-scale phenomena such as dark energy. Unfortunately, they would also lead to large deviations in solar system physics. For instance, they would appear as fifth forces and deviate planets in their orbits around the Sun. This can be avoided if their local effects are screened. Screening mechanisms are now well understood and currently tested in the laboratory. Associated light scalar particles could also be created from photons in dense environments in the presence of intense magnetic fields. This could happen deep inside the Sun where magnetic fields can reach several Tesla. These light particles would then propagate through the interplanetary medium and penetrate the earth’s atmosphere. Detectors such as XENON1T, originally designed to detect the presence of dark matter, can be used to track the passage of these elusive light particles. In 2020, the XENON1T experiment claimed to have seen an unexpected signal.