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What is matter made of? Scientists have been trying to answer this question for thousands of years. The concept of the atom—the tiniest fragment of a substance that still retains the… Read More →

What are cells made of? Biologists have been studying cells since the mid-1600s, when Robert Hooke viewed a slice of cork through a microscope and coined the word "cell" to describe the… Read More →

How are polar bears related to pandas? For thousands of years, philosophers and scientists have tried to organize and understand, or classify, the relationships among Earth's animals and… Read More →

Since prehistoric times, people have been fascinated by electricity and magnetism. Ancient people marveled at the auroras—streaks of colored light that appear in the night sky near the poles. Read More →

Outraged people claimed that Darwin's theory had made humans the relatives of monkeys. Scientists were sure that species changed over time, but no one could explain how. In the 1800s, Charles Read More →

If a black dog and a white dog have puppies, what color will the puppies be? Genetic scientists have been trying to answer this question for hundreds of years. Genetics is the science of… Read More →

Since prehistoric times, people have wondered what causes disease. Early people blamed evil spirits. Later, disease was thought to be caused by an imbalance of bodily fluids. By trial and… Read More →

For hundreds of years, people found the fossils of ancient sea creatures at the tops of tall mountains. Scientists puzzled over this problem. A fish couldn't have swum up a mountain. And how… Read More →

Since prehistoric times, people have wondered how the universe works. Early scientists studied how forces affect objects and watched how heavenly bodies move. In 1687 Isaac Newton published a Read More →