The earlier chapters in this book have dealt with the properties of water, buffers, amino acids and proteins. This theoretical background will be useful throughout any purification procedure, providing a framework of knowledge to help answer some of the problems that may arise. The knowledge that is specific to your protein of interest can be acquired by reading the relevant scientific papers. However, the best way to become acquainted with your target protein is to undertake a number of small scale procedures before embarking on the purification process. This holds true for the operator enriching a target from a cellular extract as well as the operator using a recombinant protein expression and purification kit. The information obtained from this ground work will pay dividends when decisions have to be made on the choice of resin and starting/elution conditions for chromatography.