AtomX is a service launched by Euronext in October 2015 designed for investors looking to bilaterally negotiate trades. It will allow users to customize and trade options and futures, which will be cleared through LCH Clearnet, in the same clearing pool as the rest of Euronext's derivatives positions. The new service will also allow clients to offset positions negotiated outside the central order book against position in the COB, so they pay less margin. AtomX will also attempt to develop additional on-exchange capabilities for users.
The launch comes at a time when regulators are calling for more transparency and mitigation of the systemic risk posed by over-the-counter derivatives. At the same time market participants are looking for more efficiencies in portfolio management. 
In addition to the standard financial derivatives contracts available in Euronext’s central order book, AtomX will offer more than 900 flex contracts where clients can change the standard terms, although expiration dates are currently limited to the third Friday of the month.