This book aims to discuss the optical properties of milk based on light propagation and random lasing. Light propagation in milk is measured through absorbance, transmission, reflectance, and fluorescence spectra. Near infra-red (NIR), visible (VIS), and Fourier transform infrared (FTIR) techniques are used to compare light propagation in milk. Three different spectrometry methods are used to analyze milk fat contents based on absorbance and transmittance spectra. The book also reveals that the newly opened milk bottle has higher light absorbance and lower light transmission than fermented milk. The optical properties of milk from animal, plant, and human sources are differentiated based on light propagation and random lasing. The absorbance and fluorescence of various milk samples in the wavelength range 350 nm to 1,650 nm are measured, showing different results for each milk due to different fat content. Statistical analysis using principal component analysis (PCA) is used to analyze the reliability and validity of the absorbance and fluorescence data. The e-book highlights the importance of assessing milk's optical properties