Dr. Paul Kalanithi touched countless lives, first as a neurosurgeon, then as a patient himself. He wrote with brutal and beautiful honesty about facing his own death.

Dr. Kalanithi died Monday night from lung cancer. Like many lung cancer patients, the 37-year-old Stanford neurosurgeon never smoked. Months after his 2013 diagnosis, Dr. Kalanithi wrote an Op Ed in the New York Times explaining what it was like to look at his own scans.

His personal experience resonated with thousands upon thousands of people, and he received hundreds of emails from people.

Dr. Kalanithi leaves behind his wife Lucy and a baby daughter named Cady.