A method of screening protein crystal growth conditions with picogram to microgram amounts of protein in picoliter or nanoliter volumes is provided. A preferred method comprises a microarray with a plurality of microchambers in the microarray. A protein solution is placed into the micro-chambers by an automated dispensing mechanism. The protein crystal growth conditions of each of the micro-chambers is adjusted so that the protein crystal growth conditions in at least two of the micro-chambers differs. Crystallization of the protein solution in the micro-chambers is effected. For example, crystallization can be effected by a precipitate solution and/or placing an oil barrier over the protein solution. Protein crystal growth in the micro-chambers is then observed.