Diplococci are a type of bacteria that appear as pairs of spherical cells. They are classified as gram-positive or gram-negative based on their cell wall structure. Common examples include Streptococcus pneumoniae, which can cause pneumonia, and Neisseria gonorrhoeae, responsible for gonorrhea. These bacteria reproduce by binary fission, where one cell divides into two. Diplococci can be found in various environments, including the human body, where they may be part of the normal flora or cause infections. Their arrangement in pairs is a key characteristic that helps in their identification under a microscope.