1. Introduction.- 1.1 Perturbed Angular Distribution Techniques.- 1.2 Perturbed Angular Correlation Techniques.- 1.3 Nuclear Magnetic Resonance on ?-Emitting Nuclei.- References.- 2. Hyperfine Interactions of Excited Nuclei in Atomic Systems.- 2.1 Free Atoms in Flight-The Recoil Distance Method.- 2.2 Atoms in Gases.- 2.3 Magnetic Decoupling Measurements in Vacuum.- 2.3.1 Fields Parallel to the Quantization (Beam) Axis.- 2.4 New Methods and Future Directions.- References.- 3. Hyperfine Interaction Studies in Nuclear Physics.- 3.1 Overview.- 3.2 Hyperfine Hamiltonian and Nuclear Moments.- 3.3 Laser Spectroscopy and Hyperfine Structure of Exotic Nuclear States.- 3.4 Nuclear Moments of High-Spin States.- 3.5 Magnetic Moments of Simple Shell-Model Configurations.- 3.6 Hyperfine Interactions in Nuclear ? Decay.- References.- 4. Hyperfine Interactions of Defects in Metals.- 4.1 Relevant Solid State and Nuclear Physics Aspects.- 4.2 Hyperfine Investigations of Defects.- References.- 5. Electric Quadrupole Interaction in Noncubic Metals.- 5.1 Electric Quadrupole Hyperfine Interaction.- 5.2 Experimental Methods.- a) Nuclear Resonance Methods.- b) Perturbed Angular Correlation (Distribution) Methods.- 5.3 Experimental Data and Systematic Trends.- 5.4 The EFG in Metals.- 5.4.6 Pressure and Concentration Dependence.- 5.5 Conclusion.- 5.6 Appendix.- Table of Experimental Data on Quadrupole Interaction in Noncubic Metals.- References.- 6. ? Emitters and Isomeric Nuclei as Probes in Condensed Matter.- 6.1 Theory.- 6.2 Experimental Methods.- 6.3 Metals.- 6.4 Insulators.- 6.5 Tabular Summary.- References.mehr