 Welcome to this tutorial where we will learn how to search for real reactions using the chemical structure information encoded by an INCHI key. An INCHI key is a computer readable representation of the structure of a chemical compound. It is derived from the International Chemical Identifier or INCHI Standard, a textual representation that describes a molecule in terms of different layers of information. Formula, atom connection, hydrogen position and charge. The condensed INCHI key is a hashed version of the full INCHI, which is designed for easy web and database searches of chemical compounds. An INCHI key is composed of 27 characters organized in three blocks. The first block encodes information about the molecular skeleton and atom connectivity. The second information about the stereochemistry and the third block information about the charge of the molecule. This representation of the chemical structure of molecules is mainly used in programmatic access. However, the RIA website supports searches for RIA reaction participants by complete or partial INCHI key. Using the simple and advanced search and the retrieve ID mapping service interactively as well as programmatically. Let's look for RIA reactions involving Aldehido D. Glucose 6-phosphate, which is represented by this INCHI key. We copy-paste this INCHI key in the simple search box using the prefix INCHI key colon. It returns three RIA reactions. Note that the URL of the result page contains the INCHI key and can be bookmarked. We could have done the same type of query using the advanced search. To do this, we click on Advanced Search, click on All, select INCHI key and copy-paste our INCHI key. We can also query RIA with a partial INCHI key omitting the second or third block. Information on the charge of our molecule is encoded in the third block of the INCHI key. If we query with the third part omitted, we get the same steel reactions as before. The reason is that the RIA search engine bypasses the charge constraints and always returns the RIA reaction with the kebby compounds that correspond to the major micro-species at pH 7.3. This concept is explained in more detail in the guided tour to RIA's key features and web interface, which is linked below. Queries with or without the third part of an INCHI key will therefore always return the same results. If the stereochemistry of our molecule is not relevant for our search, we can search RIA using only the first part of the INCHI key. Now we get six RIA reactions. We can see that these RIA reactions share a reaction participant, which has a common molecular skeleton. If we want to have additional information on the INCHI key and the corresponding molecules, we can click on a RIA reaction. The information is found in the reaction participant section. When working with INCHI keys, it is more convenient to use the Retrieve ID mapping service, which has additional useful functionalities for this use case. We click on the Retrieve ID mapping link, select the identifier type INCHI key, copy-paste our list into the box and click on Submit. The result table contains a column with the queried INCHI keys and, what is interesting, the corresponding KEBI identifiers. The search engine performs an exact search. It does not take into account the IS-A relationships found in KEBI. We can observe that our two INCHI keys correspond to two small molecules, which participate in two RIA reactions. If the stereochemistry of our molecule is not important, we could have used a partial INCHI key. All the results shown in this tutorial will of course change regularly, depending on the evolution of biological knowledge and on progressing bio-curation efforts. Never hesitate to contact us if you have any questions or remarks and to look at our help pages and other videos. Thank you for your attention.