Chlorophyll fluorescence is a widely-used technique in plant physiology and photosynthesis research that measures the light emitted by chlorophyll molecules when they are excited by light. This technique provides valuable information about the efficiency of photosynthesis, stress responses, and overall health of plants. By analyzing the fluorescence emission spectrum, researchers can gain insights into factors such as photosynthetic efficiency, pigment composition, and the presence of environmental stressors. Chlorophyll fluorescence is non-invasive and can be used in the field or in laboratory settings to study a wide range of plant species and environmental conditions.