Nowadays, biologists use biological data sources and tools to find relevant information for their research. However, with the explosion of the amount of online accessible data and tools, finding the relevant sources and retrieving the relevant information is not an easy task. Further, often information from different sources needs to be integrated. The vision of a Semantic Web alleviates these difficulties. The Semantic Web is an extension of the current Web in which information is given a well-defined meaning by annotating Web content with ontology terms. In this paper we discuss the Semantic Web vision and focus on an important technology, ontologies, that is needed to make this vision happen.