01 | Byron | Foundation || Cardano is a third-generation blockchain, created from the ground up using research, peer-review, and a rigorous formal development model. The story began in 2015, with a vision of addressing the three strategic challenges facing all blockchain networks: scalability, interoperability, and sustainability. The Byron era also saw the delivery of the Daedalus wallet, IOHK's official desktop wallet for ada, as well as Yoroi, a light wallet from IOHK's sister company Emurgo designed for quick transactions and day-to-day use.

02 | Shelley | Decentralisation || Following on from the Byron era, the Shelley era of Cardano is a period of growth and development for the network. Unlike the Byron era, which began at a single point in time when the mainnet was launched, the transition to Shelley is designed to achieve a smooth, low-risk transition without service interruptions. The Shelley era encompasses the critical early steps in Cardano’s journey to optimize decentralization – and like any first steps, these will be gradual but significant. During the Byron era the network was federated, but as the Shelley era progresses more and more nodes will shift towards being run by the Cardano community. Once the majority of nodes are run by network participants, Cardano will be more decentralized and enjoy greater security and robustness as a result. Come the end of the Shelley era, we expect Cardano to be 50-100 times more decentralized than other large blockchain networks, with the incentives scheme designed to reach equilibrium around 1,000 stake pools.

03 | GOGUEN | Smart contracts || With the integration of smart contracts, the Goguen era represents a big step forwards in capability for the Cardano network. Where the Shelley era decentralizes the core of the system, Goguen adds the ability to build decentralized applications (DApps) on Cardano's solid foundation of peer-reviewed research and high-assurance development. The work for Goguen has been under way in parallel with Shelley, and when complete will allow users from technical and non-technical backgrounds to create and execute functional smart contracts on the Cardano network. One of the goals for the Goguen era has been the creation of Plutus, a purpose-built smart contract development language and execution platform using the functional programming language Haskell. The Goguen era also encompasses work to make Cardano accessible to wider audiences via Marlowe, allowing financial and business experts with no previous technical knowledge to create smart contracts.As well as adding functionality in the form of smart contracts, Goguen will also see improvements to the core Cardano offering. Most significantly, the addition of a multi-currency ledger will extend the usefulness of Cardano even further, enabling users to create new natively-supported tokens. This will allow the creation of fungible and non-fungible tokens, supporting the creation of new cryptocurrencies on Cardano as well as the tokenization of many types of digital and physical assets. Another benefit will be easier integration of smart contracts and DApps involving multiple cryptocurrencies. The Goguen era represents a step change in the abilities of Cardano, opening the way to the development of enterprise-level, mission-critical, decentralized smart contract applications, with even more exciting things to come during the Basho and Voltaire eras.

04 | BASHO | Scaling || The Basho era of Cardano is an era of optimization, improving the scalability and interoperability of the network. Whereas previous development eras focused on decentralization and new functionality, Basho is about improving the underlying performance of the Cardano network to better support growth and adoption for applications with high transaction volume. One of the core developments of Basho will be the introduction of sidechains: new blockchains, interoperable with the main Cardano chain, with immense potential to extend the capabilities of the network. Basho will also see the introduction of parallel accounting styles. While the main Cardano blockchain will continue to use a UTXO model, the ability to support and switch between UTXO and account-based models will be added using sidechains. The result will be greater interoperability for Cardano, as well as the ability to support new kinds of use cases on the network. Overall, the Basho era will see Cardano become one of the most high performance, resilient, and flexible blockchain platforms in the industry. This will provide a network infrastructure with the capability to scale in a sustainable, secure way, as well as the ability to add new functionality without compromising the reliability at the core of the network.

05 | VOLTAIRE | Governance || The Voltaire era of Cardano will provide the final pieces required for the Cardano network to become a self-sustaining system. With the introduction of a voting and treasury system, network participants will be able to use their stake and voting rights to influence the future development of the network. For the Cardano network to become truly decentralized, it will require not only the distributed infrastructure introduced during the Shelley era but also the capacity to be maintained and improved over time in a decentralized way. To that end, the Voltaire era will add the ability for network participants to present Cardano improvement proposals that can be voted on by stakeholders, leveraging the already existing staking and delegation process. To fund the future development of the network, Voltaire will also see the addition of a treasury system, whereby a fraction of all transaction fees will be pooled to provide funds for development activities undertaken following the voting process. When both a voting and treasury system are in place, Cardano will be truly decentralized and no longer under IOHK's management. Instead, Cardano’s future will be in the hands of the community, who will have everything they need to grow and evolve Cardano from the secure, decentralized basis established by IOHK.