Calcium (Ca, Atomic Number: 40), is an essential element for all living organisms. In human, Calcium ion (Ca2+) is released from bone to bloodstream and its level in serum is tightly controlled (8.4-11.4 mg/dL). Ca2+ acts as second messenger and plays many biological roles in signal transduction, gene expression, muscle contraction, synaptic plasticity and hormone release. Recent studies have found that dysregulation of calcium homeostasis leads to health problems, such as Alzheimer's Diseases and Parkinson's Disease, etc. The Calcium Fluorometric Assay kit provides an easy and quantitative method to measure Calcium in various biological fluids. Low concentration of N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) is included in the assay and used to pre-treat samples to eliminate interference from other di-valent metals such as Zinc. The assay is based on the ability of our proprietary probe that binds specifically to Calcium cations generating a high fluorescence signal. The fluorescence is directly proportional to the amount of calcium, which can be quantified by measuring the generated fluorescence (Ex/Em= 500/530 nm) using a microplate reader. This assay kit provides an add-and-read, non-radioactive, and high-throughput adaptable assay suitable for Calcium detection. The assay is rapid (less than 10 min) and sensitive (Limit of Detection: <0.1 µM).