Today, mobile technology fosters in-situ digital content creation and retrieval. In response to this shift, this thesis introduces two novel in-situ mobile scenarios: 1) in-situ experiential multimedia article generation and 2) situational information retrieval during procedural tasks. Leveraging a human-centered iterative design process, this thesis crafts multimodal mobile interactions and workflows for seamless in-situ execution for the scenarios and prototypes them for validation. Furthermore, this thesis conceptualizes these interactions and workflows as two human-natural activities, Look-And-Tell and Show-And-Ask, to develop a framework for in-situ mobile usage by combining them.