The Reactome molecule Event page provides a detailed description of each molecule that participates in a Reactome reaction. This description includes (where applicable) a link to its sequence, links to the corresponding molecule in other databases (ie: Ensemble and Locus Link, ChEBI), the Reference entity (i.e. Reactome's reference database identifier), the subcellular location at which molecule is functioning, the organism in which the molecule functions, a list of any Reactome complexes that include the molecule, and a list of processes within Reactome in which the entity had been shown to be involved. In addition, all Reactome reactions in which the molecule takes part will be highlighted in the Reaction Map.  The reaction arrows are color coded to describe the role of the given molecule in the reaction. Red indicates that the molecule functions as an input in the reaction, Green = output,  Yellow = both input and output, Blue = catalyst and Violet = input and catalyst. A description of human Cdc2 is shown below  (the "participates in process" section has been truncated for viewing purposes):

Here, one can further click to access the 'Reference Entity' page for this molecule. This provides (a)details as to the various synonyms by which the molecule is known, (b) external links to established reference databases with information on this entity, and, (c) if it is a "small molecule", a chemical fingerprint of the molecule. The chemical fingerprint describes the type and number of chemical groups that this molecule contains. An example of a fingerprint for ATP is shown below:

Every small molecule in Reactome has a verified structure file (in MOL format) that is 'fingerprinted' by a set of molecular groups. Clicking on any of the group names in the above Chemical fingerprint generates a list of all small molecules in Reactome that contain this substructure. The set of chemical groups used in this fingerprinting procedure will expand in parallel with our process annotations to maintain an adequate descriptive level of those structures involved in our reactions. Complexes are also described on separate pages.