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Discovery of Cells 7th Grade Science What is a CELL? • Cell – the basic unit of all living things. • Cells are SO tiny… they are not visible to the naked eye. Robert Hooke – discovered ‘cells’ • Using a microscope, Hooke discovered small boxes in a piece of cork. • He called these CELLS. • He continued his work by examining mainly plants. He thought cells were found only in plants. Cork cells… resembles a honeycomb. Anton van Leeuwenhoek • Using a microscope , began to examine different animals. • He looked at pond scum, blood cells from fish, birds, and frogs, and blood from humans. • He was the first person to discover bacteria AND determined cells were in both, plants and animals. Pond Scum The Cell Theory • All organisms are composed of one or more cells. • The cell is the basic unit of life in all living things. • All cells come from existing cells.