This spring, the National Institutes of Health will start recruiting participants for one of the most ambitious medical projects ever envisioned.

The goal is to find one million people in the United States, from all walks of life and all racial and ethnic groups, who are willing to have their genomes sequenced, and to provide their medical records and regular blood samples.

They may choose to wear devices that continuously monitor physical activity, perhaps even devices not yet developed that will track heart rate and blood pressure. They will fill out surveys about what they eat and how much.

If all goes well, experts say, the result will be a trove of health information like nothing the world has seen. The project, called the All of Us Research Program, should provide new insights into who gets sick and why, and how to prevent and treat chronic diseases.