The scientists wanted to figure out how many tiny parts of diatoms, called frustules, are needed to identify them in a lake in Indonesia. They collected sediment samples from different depths and counted frustules in groups of 100, 200, 300, 400, 500, and 600. They found that after counting at least 300 frustules, they could identify the diatoms accurately. This means that for studying the history of the lake, 300 frustules are enough to tell which diatoms are present.