Let's understand how a simple NMR signal is generated:---1. We have a sample, like water, which contains hydrogen atoms (protons). Each proton acts like a tiny magnet.---2. We place this water sample inside a very strong external magnet. All the tiny proton magnets in the water mostly align themselves with this strong external magnetic field, either 'up' or 'down'. A few more will be 'up' than 'down'.---3. We then send a short pulse of radio waves (like the radio signals your phone uses) into the sample. If the radio waves are at a specific frequency (called the resonance frequency), they will 'flip' some of the 'up' protons to the 'down' state.---4. When the radio pulse is turned off, these flipped protons quickly relax back to their original 'up' state. As they flip back, they release a tiny bit of energy in the form of a radio signal.---5. A receiver coil detects these emitted radio signals. The frequency and strength of these signals tell us about the chemical environment of the hydrogen atoms in the water.---6. For example, in a more complex molecule, protons in different parts of the molecule will 'flip' and 'relax' at slightly different frequencies, allowing us to map the molecule's structure.---Answer: NMR detects specific radio signals emitted by atomic nuclei as they return to their original alignment after being disturbed by radio waves in a strong magnetic field.