Chiral Induced Spin Selectivity (CISS) is a phenomenon where chiral materials act as spin filters for electron transport, influencing the spin polarization of electrons. Since its discovery in 1999, CISS has been studied extensively, revealing its connection between chiral symmetry and electron spin. Recent experiments show that displacement currents from charge polarization of chiral molecules can lead to spin polarization without net charge flow. CISS has implications for various fields, including physics, chemistry, and biology, and is relevant to understanding the homochiral nature of life. This review discusses methods for measuring CISS, including photoelectron spectroscopy, electron transport, charge polarization, and other techniques. It covers molecules and materials known to exhibit CISS, such as DNA, helicenes, proteins, and various inorganic materials. General trends and structure-property relationships are analyzed, and theoretical models for CISS are presented. The review also explores CISS implications in spintronics, enantioseparations, chemical reactions, and biology, highlighting its potential applications. CISS is measured through various techniques, such as Mott polarimetry, ultraviolet photoelectron spectroscopy, conductive probe atomic force microscopy, scanning tunneling microscopy, magnetoresistance studies, and electrochemical tunnel junctions. These methods reveal spin-dependent electron transport and charge polarization in chiral systems. The CISS effect is also observed in spin-dependent charge transfer, spin exchange interactions, and spin polarization induced by charge polarization. The review emphasizes the importance of CISS in understanding spin transport, charge transfer, and magnetic properties in chiral systems. It discusses the role of CISS in biological processes, such as redox reactions and protein stability, and its potential applications in spintronic devices and enantioselective separations. The review concludes with a critical assessment of the CISS field, highlighting its significance and future directions.Chiral Induced Spin Selectivity (CISS) is a phenomenon where chiral materials act as spin filters for electron transport, influencing the spin polarization of electrons. Since its discovery in 1999, CISS has been studied extensively, revealing its connection between chiral symmetry and electron spin. Recent experiments show that displacement currents from charge polarization of chiral molecules can lead to spin polarization without net charge flow. CISS has implications for various fields, including physics, chemistry, and biology, and is relevant to understanding the homochiral nature of life. This review discusses methods for measuring CISS, including photoelectron spectroscopy, electron transport, charge polarization, and other techniques. It covers molecules and materials known to exhibit CISS, such as DNA, helicenes, proteins, and various inorganic materials. General trends and structure-property relationships are analyzed, and theoretical models for CISS are presented. The review also explores CISS implications in spintronics, enantioseparations, chemical reactions, and biology, highlighting its potential applications. CISS is measured through various techniques, such as Mott polarimetry, ultraviolet photoelectron spectroscopy, conductive probe atomic force microscopy, scanning tunneling microscopy, magnetoresistance studies, and electrochemical tunnel junctions. These methods reveal spin-dependent electron transport and charge polarization in chiral systems. The CISS effect is also observed in spin-dependent charge transfer, spin exchange interactions, and spin polarization induced by charge polarization. The review emphasizes the importance of CISS in understanding spin transport, charge transfer, and magnetic properties in chiral systems. It discusses the role of CISS in biological processes, such as redox reactions and protein stability, and its potential applications in spintronic devices and enantioselective separations. The review concludes with a critical assessment of the CISS field, highlighting its significance and future directions.