part of anatomical structure morphogenesis animal organ morphogenesis histogenesis and organogenesis Morphogenesis of an animal organ. An organ is defined as a tissue or set of tissues that work together to perform a specific function or functions. Morphogenesis is the process in which anatomical structures are generated and organized. Organs are commonly observed as visibly distinct structures, but may also exist as loosely associated clusters of cells that work together to perform a specific function or functions. GO:0009887 biological_process animal organ development