invivo

In vivo, Latin for "within the living," refers to processes, experiments, or measurements conducted inside a living organism. The term is used across biology and medicine to distinguish whole-organism studies from in vitro (in glass) or ex vivo (outside the organism but using tissues) approaches. In vivo work aims to observe normal physiology, disease progression, or therapeutic effects in a context that includes systemic interactions such as metabolism, immune response, and organ crosstalk.

Applications include pharmacology and toxicology (assessing drug absorption, distribution, metabolism, elimination, and toxicity in whole organisms); physiology and developmental biology (examining how processes unfold under intact regulation); genetics and gene therapy (delivering vectors or editing genomes in living animals or humans); and disease research (modeling cancer, neurodegenerative disorders, infectious diseases). In humans, clinical trials are the primary form of in vivo study.

Techniques include use of animal models (mouse, rat, zebrafish, nonhuman primates), telemetry and wearable devices, and noninvasive imaging methods such as MRI, PET, and ultrasound to monitor biology in real time; intravital microscopy to visualize living tissues; and in vivo gene delivery or editing approaches. Data from in vivo studies are often complemented by in vitro or in silico experiments to build a fuller understanding.

Advantages of in vivo studies include greater physiological relevance and ability to study systemic interactions and pharmacokinetics. Limitations include species differences that may limit extrapolation to humans, ethical and regulatory considerations, higher cost, and greater variability. Rigorous oversight by institutional review boards and animal care and use committees governs human and animal in vivo research, with guidelines to minimize suffering and ensure scientific value.