Smithsonian 4 Pack Micro Science Kits provides endless hours of science fun. Smithsonian Prehistoric Sea Monsters, Hatch your own Prehistoric Pets, Witness a 220-Million Year Old Species Come to Life. Smithsonian Magic Rocks - Instant Crystal Growing Kit, Create a Brilliant Underwater Garden, Rocks Grow to Different Heights up to 4" (10 cm). Smithsonian Newtons Cradle- Demonstrates Conservation of Linear Momentum, Swing One Ball, or Two and Observe Equal Reaction on The Other End. Smithsonian T. Rex Fossil - Learn About Dinosaurs and Paleontology, over 10" (25.4 cm) long Includes 4 Micro Science Kits: Sea Monsters, Magic Rocks, Newtons Cradle and Fossil T. Rex.