Functional protein microarray is an important tool for high-throughput and large-scale systems biology studies.Besides the progresses that have been made for protein microarray fabrication,significant advancements have also been achieved for applying protein microarrays on determining a variety of protein biochemical activities.Among these applications,detection of protein binding properties,such as protein-protein interactions (PPIs),protein-DNA interactions (PDIs),protein-RNA interactions,and antigen-antibody interactions,are straightforward and have substantial impacts on many research fields.In this review,we will focus on the recent progresses in protein-protein,protein-DNA,protein-RNA,protein-small molecule,protein-lipid,protein-glycan,and antigen-antibody interactions.We will also discuss the challenges and future directions of protein microarray technologies.We strongly believe that protein microarrays will soon become an indispensible tool for both basic research and clinical applications.