3D printing was developed in 1984 and allows digital objects to be created from 3D model data through an additive process of layering materials. The document discusses the history and mechanisms of 3D printing, including modeling an object digitally or through scanning, then slicing the model into layers to guide the printer. Common 3D printing technologies build objects through extruding thermoplastics, photopolymerization, powder binding, or sheet lamination. Applications exist in industries like engineering, healthcare, and consumer products due to advantages like customization and complexity. However, 3D printing also faces limitations such as a narrow choice of materials and size constraints.