Science is the process of exploration and discovery about how the world works. Science involves asking questions, formulating ideas, making observations, gathering and interpreting data, challenging assumptions, and revising ideas based on the data. Science is systematic and requires careful, deliberate and organized procedures. Scientific ideas and understanding can change and deepen with new evidence. The development of scientific knowledge usually takes a long time. Scientists spend a lot of time rechecking and duplicating their observations, carefully writing up their results and then publishing them. Science also is iterative—meaning it circles back on itself so that useful ideas are built upon and used to learn even more. Most scientific discoveries are made by teams of researchers. While a single scientist may work alone, he/she is still dependent upon the work of scientists who have gone before and the community of scientists that review and validate the discoveries. Science is not a process that is totally objective. Scientists like all people have values and biases that can influence what they do, how they do it and what they conclude. Scientists rely on the scientific community to review their work—in a process known as peer review—to minimize biases and validate scientific work and understanding. Science is not a process that is perfect.