Recent observational results from space- and ground-based telescopes have demonstrated that a unified approach to the relationships between solar and stellar magnetism is necessary to advance our understanding of magnetic fields. The Proceedings of IAU Symposium 354 present recent results and discussions of emerging topics, including: magnetic field diagnostics using high-resolution observation; initial data from ALMA, Chinese Radio Spectroheliograph and other instruments; the detection of stellar magnetospheres; and the detailed mapping of magnetic fields on the surface of stars using new unique instrumentation. These observations stimulate comparisons of solar and stellar results, and improve our understanding of how surface magnetic structures and their evolution are related to the generation of magnetic fields by dynamos in solar and stellar interiors. This volume benefits graduate students and researchers interested in the recent advances and key problems of solar and stellar magnetic fields, and their impacts on planetary atmospheres.