This book presents new research on the leading edge of neurochemistry. Chapter One provides recent developments in understanding the neurochemistry of endogenous sulphur-containing amino acids as neuromodulators, metabolic intermediates and potential toxins. Chapter Two reviews the latest advances in the development of approaches for the qualitative and quantitative analysis of monomers and aggregates of β-amyloid peptides and encompasses separation methods such as chromatography, slab gel electrophoresis, capillary electrophoresis and lab on chip. In addition, it presents the authors' latest developments in a capillary electrophoresis with laser-induced fluorescence detection method for the analysis of aggregates of β-amyloid peptides. Chapter Three reviews the most significant improvements recently made in monoamines analysis and detection, using capillary and ultra-HPLC and will discusses the advantages and pitfalls of those approaches applied to brain monoamine monitoring.