Up to 50,000 people are being asked to come forward in Wales for a major medical research study, aimed at cutting future disease and illness.
First Minister Rhodri Morgan launching Biobank Cymru
Biobank Cymru, launched in Cardiff, is part of UK Biobank, which is looking for 500,000 people aged 40 to 69 to take part in a health check.
Those invited to take part will give blood and urine samples, be weighed and measured and have lifestyle interviews.
Scientists hope to track their health over the next 30 years or more.
The project aims to collect what has been called a "treasure trove" of important medical information.
It has already started in England and Scotland and is being rolled out in the rest of the UK, with the Welsh research being managed by Cardiff University, but also involving Swansea and Bangor universities.
Assessment centres have already opened in Manchester, Oxford and Glasgow.
People are being invited to take part by letter over the next six months and will be asked to consent to long-term follow-ups, as the study progresses.
It is hoped that data gathered on patients will help in the future treatment of a range of diseases, from heart disease, cancer, strokes, to arthritis and depression.
Dr John Gallacher of the department of epidemiology, statistics and public health at Cardiff University's school of medicine said: "This is a massive undertaking to improve the health of future generations.
"I do hope people will want to be a part of this historic project.
"In particular, it will provide insights into why some people get particular diseases and others do not - paving the way for prevention and better treatments."
The study will begin with volunteers living within a 10-mile radius of Cardiff before the project moves to other parts of Wales over the next five years.
Volunteers will be given lung function and blood pressure tests as part of the examination, before 90 minute interviews on health and lifestyle.
Chief medical officer for Wales, Dr Tony Jewell said it was "a fantastic opportunity for people to do something positive for the health of the next generations".
He added: "They will play a crucial role in our understanding of a wide range of serious and life-threatening illnesses and help health scientists develop measures on the prevention, diagnosis and treatment of such conditions."
The project is backed by the Welsh Assembly Government and was launched by the First Minister Rhodri Morgan.