Histology is the medical specialty devoted to the study of biological tissues. It studies the structure of these tissues at a microscopic level and enables us to understand normal and pathological functioning. It is based on tissue samples that can come from any part of the body: this can be called a tissue biopsy or a smear depending on the technique used for collection. Sometimes, the study is carried out on an entire organ, as in the case, for example, on the gallbladder during a cholecystectomy. Implemented by a pathologist, histology is particularly widely used in cancer pathology to determine whether a tumor is malignant or not, or to identify to what extent it has spread.