into the NMR properties of fluids in porous media laid a firm fundamental basis for interpretation of NMR relaxation in later NMR logging data. These developments are described in Part 1. The next technological development was the invention, at Los Alamos, of permanent magnet/pulsed radio frequency (RF) NMR well logging in 1978. This technique used permanent magnets to produce a B 0 field in the geologic formations surrounding the borehole and used pulsed RF to manipulate the nuclear spin system of formation fluids. Laboratory tests of this technique were followed by a proof-of-principle demonstration in 1983. This is described in Part 2. The Los Alamos discovery was followed, in the 1980’s by two new techniques, one at NUMAR (now Halliburton) and the other at Schlumberger. Each used the permanent magnet/pulsed RF concept, but implemented it in different magnet/coil configurations. Both give valuable geophysical information and are in regular commercial use in the petroleum industry. The NUMAR and Schlumberger stories are told in Parts 3 and 4, respectively. These new logging tools have led to new procedures to extract information on properties of reservoir fluids. These are described in Part 5. Part 6 describes a new development, NMR logging-while-drilling (LWD), in which the NMR instrument is an integral part of the drill string and is located just above the drill bit. Table I-1 gives a timeline of these developments.