1.1 Introduction1.2 Why Is Hyperspectral Imaging?1.3 Two Principles for Hyperspectral Imaging1.4 What Are the Issues of Hyperspectral Imaging?1.5 Determination of p by Virtual Dimensionality via Pigeon‐Hole Principle1.6 Order Determination of Low Rank and Sparse Matrices by Virtual Dimensionality via Pigeon‐Hole Principle1.7 Band Selection by Pigeon‐Hole Principle1.8 Band Selection by a Hyperspectral Band Channel via Pigeon‐Hole Principle1.9 Band Sampling via Pigeon‐Hole Principle1.10 Spectral Unmixing via Orthogonality Principle1.11 Target Detection by Orthogonality Principle1.12 Anomaly Detection by Orthogonality Principle1.13 Endmember Finding by Orthogonality Principle1.14 Low Rank and Sparse Representation by OSP via Orthogonality Principle1.15 Hyperspectral Classification1.16 ConclusionReferences