Observation is frequently called the most basic of all the scientific skills. Ideally, observations should not include any assumptions, interpretations, opinions, or conclusions on the part of the observer. You should never attempt to explain why something happened or what something is when you make an observation. Observations should be limited to what can be perceived through your senses. In everyday life, people normally do not bother to distinguish between observations and inferences. In science, however, it is important to understand the difference between an observation and an inference. In particular, we must be careful not to state an inference as if it were an observation. Inferences masquerading as observations can be problematic, both in science and in the classroom. This chapter helps teach about active and passive observations.