The goal of this observational (diagnostic validation) study is to validate imaging-based biomarkers for assessing liver involvement in pediatric patients with established or suspected liver disease. The projekt involves 3 larger studies, each with specific aims specified in detailed description below. The main study (study 1) compares imaging-based biomarkers-with liver biopsy to evaluate their correlation with histologically confirmed liver disease, including fibrosis, inflammation, and steatosis. The main question the overall project aims to answer is: • Can multiple novel imaging-based biomarkers, such as shear wave elastography (SWE), shear wave dispersion (SWD), and attenuation imaging (ATI), be used for detailed, non-invasive liver characterization in children, and if so, how should they be used?