1. Microorganisms (1674)
Microscope lens grinder Anton Van Leeuwenhoek accidentally discovers microorganisms in a drop of water. He observes sperm, bacteria and red blood cells.

2. The Cell Nucleus (1831) While studying an orchid, botanist Robert Brown identifies a structure within the cells that he terms the "nucleus."

3. Archaea (1977) Carl Woese discovers bacteria are not the only simple-celled prokaryotes on Earth. Many of the organisms classified in the new kingdom of Archaea are extremophiles.

Grade Level : 6 - 12

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