This lecture discusses the objective of inventory, which is to scale elementary processes, focusing on boundaries and the calculation of the life cycle inventory. It covers examples comparing a brownie recipe with an inventory, the prerequisites for life cycle inventory calculation, and examples of inventory calculations for disposable cups and coffee consumption. The lecture also explains the subdivision of the life cycle inventory calculation into four steps, including data collection, scaling to the functional unit, calculation of elemental flows, and aggregation of scaled elemental flows.