These Proceedings present the most recent results from the highly successful international solar space missions (SOHO, CORONAS-F, TRACE, RHESSI, YOHKOH) and ground observatories around the Earth, reported at the IAU Symposium 223 held in St Petersburg, Russia, June 14-19, 2004. These include discussions of the current theories of solar dynamics and activity, new constraints provided by the multi-wavelength observations of the Sun from the interior to the heliosphere, as well as discussions of future coordinated plans and efforts of multi-wavelength investigations of the Sun. The Proceedings contain the material of seven plenary sessions and three round-table discussions: Relationship between solar and stellar activities, Coordination of observations and data analysis for CORONAS-F, SOHO, and related projects, and Analysis and interpretation of historical solar activity data. This volume includes 26 review papers covering all aspects of solar activity studies, and more than 200 contributed papers.
