Vlad Zamfir, an Ethereum researcher and co-founder of Smart Transactions (STXN), has created a "time machine" that allows Ethereum users to reverse "smart transactions" on the blockchain, which makes certain transactions less immutable. Smart transactions also allow users to set specific conditions for transaction times and execution. Similar to the way Gmail allows users to cancel sending emails, the feature will be supported on blockchains compatible with the Ethereum Virtual Machine.