SAN FRANCISCO — The spectacular rise and fall of health start-up founder Elizabeth Holmes still prompts questions about how it could have happened.

Holmes, who rocketed to fame nearly a decade ago, said she founded Theranos to revolutionize blood testing. But she toppled from grace nearly as quickly after investigations revealed her company’s blood-testing technology was not working as advertised.

Holmes is now charged with two counts of conspiracy to commit wire fraud and 10 counts of wire fraud — charges that allege she knowingly misled investors and patients about the capability of her company’s technology to defraud them.

Her trial began Sept. 8 in federal court in the Northern District of California in San Jose. Here’s what you need to know.