Layers of Learning Unit 4-19 starts with the history of technology since 1900. It includes the airplane, plastics, synthetic fertilizers, assembly line, penicillin, electrification, electron microscope, washing machine, integrated circuit, and the internet. Next in geography continue studying your home state with lots of projects about your local government, economy, and natural resources. Then learn about habitats in science including ecological succession, niche, and biomes. Last in the arts learn about some of the great buildings of the world including the pyramids, the Parthenon and columns, Florence cathedral and domes, the Colosseum, the Pantheon, the leaning tower of Pisa, Notre Dame Cathedral, the Taj Mahal, the Sydney Opera House, and more. In each unit you'll find a recommended library list, important background information about each topic, and lots of activities to choose from for kids of all ages. Sidebars include a bunch more ideas including Additional Layers, Fabulous Facts, On The Web, Writer's Workshop, Famous Folks, and Teaching Tips. Printable maps and worksheets are included at the end of each unit and may be printed as often as needed for your family or class.