Reference, news, magazine, and review sources are good places to start your research so you can get a general overview of your topic.
Encyclopedias and Dictionaries: General or specific reference sources that will provide background details on your topic.
Science News Resources: Current research findings on your topic.
Review Articles, Books, and Magazine Articles: A higher level (yet still general) discussion of your topic.
Popular science magazines can be a good introduction to a topic, as they are easy to read but generally have information that is supported by peer-reviewed research. They may even be discussing a specific research article in popular language.
Remember, if your instructor has asked you to use academic or peer-reviewed sources, you don't want to cite this type of source for your assignment. But it is useful for getting some ideas about your topic.
Here are some popular science magazines, try searching for your topic in each:
Gale Encyclopedia of Science