In this design and technology lesson, students learn about 3D printing, a process used to create prototypes and various objects from plastic by assembling them layer by layer. The lesson explains the steps involved in 3D printing, including designing a 3D model using CAD (Computer Aided Design) software, saving it as an STL file, and converting it for printing. Students also explore the diverse applications of 3D printing, such as creating toys, bowls, and home decor, and post-processing techniques like sanding to finish printed models.