Dense packings of identical hard spheres inside a cylindrical tube mimic the periodic structures of a variety of columnar systems such as nanotube-confined fullerenes and colloidal crystal wires. A rich variety of corresponding densest possible structures, many of which are helical (including the well-known double helix), have been predicted from the computational approach of simulated annealing. This book presents a comprehensive description of a recently published practical method of sequential deposition for constructing and simulating all those densest possible structures as well as some novel helical structures, where the method is new and has been covered by a number of news media including ScienceNow, PhysOrg, and Le Monde. The monograph serves as a step-by-step guide for scientists, engineers, architects, and artists who would like to build or simulate those aesthetically beautiful structures in their own fields of expertise.