David Cohen made many of the first pioneering measurements in the area of biomagnetism (magnetic fields produced by the body),[1] although he was initially trained as a nuclear physicist.
To obtain clearer results, in 1969 Cohen built an elaborate shielded room at MIT, but still needed a more sensitive detector.
James Zimmerman had just developed[2] an extremely sensitive detector called the SQUID (Superconducting Quantum Interference Device).
Today, most biomagnetic measurements are of the human brain (MEG); these are made in a shielded room, using a helmet over the head containing hundreds of SQUIDs.
[6] He remains active in 2017, is on the faculty at the Harvard Medical School, and is a mentor in the MEG group at MIT's Martinos Center, located at Massachusetts General Hospital.