An experiment is a scientific and methodical procedure undertaken to make a discovery or demonstrate a known fact. It can be as simple as testing an idea, or as complicated as conducting a controlled test or investigation to test a hypothesis. The goal of an experiment can be to verify, falsify, or establish the validity of a hypothesis. It could also be to determine the efficacy of something previously untried. By experimenting, we know what the outcome is when a particular factor is manipulated. Highly controlled tests (like discovering information about subatomic particles) require complex apparatus overseen by a team of scientists.

Experiments can be of various types depending on their goal, scale, and area of study. however, for the purpose of understanding, experiments can be categorized as natural, controlled, and field experiments. A natural experiment involves making a prediction or forming a hypothesis and subsequently gathering the information. A controlled experiment is generally a lab experiment, whereas a field experiment could be either a natural or controlled experiment.

A natural experiment (also called quasi-experiment) is one that relies solely on observations of the variables of the system under study, rather than manipulation of any of the variables. natural experiments are conducted for studying designs, whenever controlled experimentation is difficult. Most of the research in geology, ecology, and astronomy is based on natural experiments. For instance, if we want to test the hypothesis "suns are collapsed clouds of hydrogen", we cannot start with a giant cloud of hydrogen, and then perform the experiment of waiting a few billion years for it to form a sun. Rather, we can observe various clouds of hydrogen in various states of collapse and can collect data we require to support the hypothesis.

A controlled experiment is the one in which an observer tests the effect of a particular variable, by changing it while keeping all other variables the same. Controlled experiments are carried out mainly for testing only one factor at a time. To conduct a controlled experiment, two groups are needed: an experimental group (exposed to the factor being examined) and a control group (not exposed to the factor). A good example of this would be an experiment to test drug effects. While all variables are kept similar (eg. age, sex, etc.) the only difference between the groups is the taking of medication. If the control group and experimental group are showing similar results, it means that the drug may be ineffective or is not showing significant therapeutic results.

A field experiment is one that cannot be carried out in the artificial and highly controlled setting of a laboratory. In-field experiments, the results are observed in a natural setting, that is, in a real-world situation. Engineers often conduct field experiments to test the performance of prototype products.

A laboratory is a room or building equipped for scientific research, or teaching, or for the manufacture of drugs or chemicals. It is also a facility that makes available controlled conditions, in which technological research, experiments, and measurement may be performed. A laboratory can also be a mobile unit that facilitates carrying out the work on the field or the site. Some common lab equipment is balance, beaker, bunsen burner, dialysis tube, dissection microscope, eye goggles, filter paper, fire extinguisher, flask, gloves, cylinder, hot plate, microscope, glass slide, mortar and pestle, ph tester, pipette, test tube, thermometer, etc. Apart from these, specific labs may have special equipment. A physics lab might contain a particle accelerator or vacuum chamber, while a metallurgy lab could have apparatus for casting or refining metals or for testing their strength.