What is the fine-grained topic of the following text: There are five general classes of printing processes: relief printing, which includes letterpress and flexography; planographic printing, which includes offset lithography, screenless lithography, collotype, and waterless printing; intaglio, which includes gravure, steel-die, and copper-plate engraving; stencil and screen printing; and electronic printing, which includes electrostatic, magnetographic, ion or electron deposition, and ink-jet printing. Only return the topic.
Types of Printing Processes