Histopathology and histomorphometry are important tools used in preclinical studies to evaluate the effects of a substance on tissue structure and function. These techniques involve the examination of tissue samples obtained from animals that have been exposed to the substance of interest.

Histopathology involves the microscopic examination of tissue samples to identify any morphological changes, such as inflammation, necrosis, or fibrosis, which can provide insights into the nature and extent of tissue damage caused by the substance. It can be used to evaluate the effects of a substance on a wide range of tissues, including the liver, kidney, lung, heart, and brain.

Histomorphometry involves the quantitative analysis of tissue samples, which can provide information on changes in tissue structure and function. It can be used to evaluate changes in tissue volume, cell number, and size, as well as changes in the thickness and density of specific tissue components, such as bone or cartilage. Histomorphometry can be used to evaluate the effects of a substance on tissues such as bone, muscle, and cartilage.

Histopathology and histomorphometry are often used in combination with other techniques, such as hematology, clinical chemistry, and imaging, to provide a comprehensive assessment of the effects of a substance on the animal. These techniques can help identify potential safety concerns related to a substance and can inform the design of subsequent studies to further evaluate safety and efficacy. They are essential tools in the preclinical safety assessment of drugs and other substances, and can help ensure the safety of these substances before they are tested in humans.