Apart from academic purposes, functional programming has found its way into a wide range of industrial applications such as aerospace, telecommunications and robotics. Pure functional languages such as Haskell, Scala, F# are becoming popular across these industries. The properties of immutability and persistency make these data structures more robust in terms of transparency, simulations and efficiency. The current chapter primarily covers functional data structures, concepts of lazy evaluation and detailed analysis of functional stacks and functional queues.