Ontologies were developed in Artificial Intelligence (AI) to facilitate knowledge sharing and reuse. Since the beginning of the nineties ontologies have become a popular research topic investigated by several AI research communities, including knowledge engineering, natural-language processing and knowledge representation. Ontologies are now ubiquitous in many intelligent information-systems enterprises; they are used in e-health and in various tasks of biological and medical sciences. Ontologies are becoming so popular in large part due to what they promise: a shared and common understanding of some domain that can be communicated between people and application systems. This paper presents some examples of the developed ontologies by the author and his colleagues at Medical Informatics and Knowledge Engineering Research Labs, Ain Shams University, Cairo, Egypt.