Tissue is a group of similar cells with shared origin performing a specific function.  In animals, the four main tissue types are epithelial, connective, muscle, and nervous. Plant tissues include epidermis, ground tissue, and vascular tissue. Histology is the study of tissue structure under a microscope, crucial for understanding cell and tissue functions. Histology relies on preparing slides through fixation, processing, embedding, sectioning, and staining.  Hematoxylin and eosin are common stains, highlighting nuclei and cytoplasm respectively. Histology finds applications in education, archaeology, disease diagnosis, and forensic investigations.