A fruit fly ovary, shown here, contains up to 20 eggs. Ripe fruit flies aren't just tiny insects that buzz around overripe fruit, they're a venerable scientific tool. Fly research has shed light on many aspects of human biology, including biological rhythms, learning, memory, and neurodegenerative diseases. Another reason fruit flies are so useful in a lab (and so effective in fruit bowls) is that they reproduce quickly. About three generations can be studied in a single month.