Scientific correspondence, papers, slides and photographs. Includes drafts and text of Thomson's unpublished autobiography; a selection of Kathleen Thomson's letters compiled originally for family circulation; notebooks, notes, drafts, slides and photographs documenting work on electron diffraction and thermonuclear reaction for which he won the Nobel Prize. Also, notes and manuscripts for talks and writings on the history and social aspects of science and documentation of his involvement with the Voluntary Euthanasia Society. The full range of Thomson's correspondence, including that on electron diffraction, has not survived.