Google has embarked on what may be its most ambitious and difficult science project ever: a quest inside the human body. Called Baseline Study, the project will collect anonymous genetic and molecular information from 175 people—and later thousands more—to create what the company hopes will be the fullest picture of what a healthy human being should be. The early-stage project is run by Andrew Conrad, a 50-year-old molecular biologist who pioneered cheap, high-volume tests for HIV in blood-plasma donations. Dr. Conrad joined Google X—the company's research arm—in March 2013, and he has built a team of about 70-to-100 experts from fields including physiology, biochemistry, optics, imaging and molecular biology. Other mass medical and genomics studies exist.