Book excerpt: Brain health is increasingly attracting attention thanks to scientific and technological advances. Investing in brain health across the life course through education, access to health care, and healthy environments is essential for meeting modern societal challenges and driving innovation. However, there is no simple, direct or global metric to measure brain health across the life. Existing efforts to quantify for instance early-life brain health rely on proxy measures such as stunting and extreme poverty, account only for individual aspects of brain functioning and fail to include direct measures of brain structure. With the intent to overcome these shortfalls, WHO convened an interdisciplinary expert group in May 2023 to discuss the development of a brain health measurement framework with a focus on early life. Meeting attendees concluded that an ideal brain health metric would combine psychometrics, neuroimaging and neuro-modelling, incorporate important brain health determinants and be able to predict relevant outcomes later in life.