This chapter surveys the emergence, technological foundations, application paradigms, and professional implications of multimodal language services in the AI era. It traces the evolution of “multimodality” from cognitive and discourse studies to contemporary large language model (LLM) and Aritificial Intelligence (AI)‑Generated Content ecosystems that integrate text, speech, image, video, and spatial signals. Core advances—multimodal LLMs, diffusion and generative architectures, agent orchestration, and retrieval‑augmented pipelines—enable cross‑modal understanding, transformation, reasoning, and generation (e.g., text‑to‑image, text‑to‑audio, and text‑to‑video, multimodal translation, adaptive subtitling, and real‑time interpreting). The chapter highlights prompt engineering as a controllability lever, redefining workflows via structured semantic specification. Application domains span education, accessibility, cultural dissemination, product localization, conferencing, Augmented Reality and Virtual Reality navigation, digital humans, and new media “media matrix” distribution models. It contrasts single‑modal baselines with multimodal semantic reconstruction focused on actionability and immersion. Governance challenges (hallucination, factuality, cultural alignment, provenance, ethical steering) motivate human–AI collaborative quality regimes. Finally, the professional role shifts from linear translation to multimodal adaptation design—encompassing product thinking, process engineering, cultural risk management, and iterative co‑creation with intelligent agents.