 Acute liver injury ALI and acute liver failure ALF are rare clinical conditions, the latter often associated with a poor outcome. To improve outcomes for these patients, clinicians need to develop a clearer understanding of the pathophysiology of this condition. Biomarkers and novel imaging techniques are vital to investigating and understanding the pathophysiology of ALI. Patients with ALI or ALF aged over 16 and due to any cause will be eligible to take part in the study. The study will involve collection of biological samples blood, urine, stool and breath from included patients once daily for up to 7 days. For patients undergoing liver transplantation, a small sample of explanted removed liver tissue will be obtained. A small subgroup of patients with paracetamol induced acute liver failure will be eligible to be included in a pilot MRI magnetic resonance imaging study, which will involve two MRI scans during the first 7 days of their admission. All patients will be recruited from the Royal Infirmary of Edinburgh. 