Tabular crystals usually have two twinned planes parallel to each other. They are formed at the very beginning of the crystallization. The crystal tends to grow at the edges and not on the main planes, forming very thin crystals of very large surface areas. Tabular crystals probably existed from very early days of silver-gelatin photography. However, it was about 1970 when emulsion engineers could make emulsions that consisted mainly of tabular crystals. Moreover, it was not until the 1980s that tabular crystals began to be used in production emulsions.