This is too general a question. What are you referring to?
Taxonomists use fossil records, morphological structures, and DNA/genetic information in order to classify organisms into different kingdoms, phylums, and classes.
Scientist classify plants as producers due their ability to make their own food. They are in the autotrophic level of the nutrient cycle.
a plant
Aristotle
mullusks
they look through a microscope
microscope
Aristotle
Aristotle
Scientist classify waves by moving through a medium and/or empty space. For example, a wall, air, water, space.
they grab a piece and scam it to see if it is
Classifications is first step to differentiation