Long-lived spin states of magnetic resonance can extend the coherence of magnetic moments beyond the time scale defined by the spin-lattice relaxation time, T1, which was once believed to be an unchangeable limit of the life span. The characteristic of this relatively new finding is the formation of an antisymmetric energy state in a coupled spin system, the so-called singlet spin state, which becomes immune to intramolecular dipolar interactions. Sequestration of nuclear spin coherence from relaxation processes could lead to several unprecedented advantageous outcomes, such as spectral narrowing, intensity enhancement, and image contrast. Unfortunately, there are limited studies on singlet and triplets in magnetic resonance and hence its logic is not yet appreciated by the community. This article summarizes the basic theories of singlet–triplet states in magnetic resonance. The fundamentals of singlet–triplet formation are explained by reviewing recent publications by forerunners in the field. Detailed calculations are given to interpret the basics, aiming to provide an overview and guide for the beginners in this field. Mathematica® is extensively utilized to simplify the product operator analysis of the pulse sequences and the conversion of spin operator matrices between the Zeeman product basis and the singlet–triplet basis. © 2014 Wiley Periodicals, Inc. Concepts Magn Reson Part A 42A: 165–181, 2013.