The book reproduces 55 of more than 300 articles written by the author, representing milestones in methods development of single-particle cryo-EM as well as important results obtained by this technique in the study of biological macromolecules and their interactions. Importantly, neither symmetries nor ordered arrangements (as in two-dimensional crystals, helical assemblies, icosahedral viruses) are required. Although the biological applications are mainly in the area of ribosome structure and function, the elucidation of membrane channel structures and their activation and gating mechanisms are represented, as well. The book is introduced by a commentary that explains the original development of concepts, describes the contributions of the author's colleagues and students, and shows how challenges were overcome as the technique matured. Along the way, the ribosome served as an example for a macromolecule with intricate structure and conformational dynamics that pose challenges for three-dimensional visualization. Toward the end of the book - bringing us to the present time - molecular structures with near-atomic resolution are presented, and a novel type of computational analysis, manifold embedding, is introduced.Single-particle cryo-EM is currently revolutionizing structural biology, presenting a powerful alternative to X-ray crystallography as a means to solve the structure of biological macromolecules. The book presents in one place a number of articles containing key advances in mathematical and computational methods leading up to the present time. Secondly, the development of the technique over the years is reflected by ever-expanding discoveries in the field of ribosome structure and function. Thirdly, as all histories of ideas, the history of concepts pertaining to this new method of visualization is fascinating all in itself.