Diatoms have silica in their shell wall. Their cell wall is called a shell or frustule. The color of the shell of the diatoms is generally transparent.Diatoms can be found in both freshwater and marine environments.The shell wall of diatoms contains silica. Shell or frustule is the name for their cell wall. The shell walls of diatoms overlap. The shells of diatoms are normally translucent in colour. Cellulose makes up most of these species' cell walls. The silica particles are found in several places in this cellulosic cell wall. As a consequence, the cell wall tends to be made of silica. The diatom comprises a diploid nucleus. Chloroplasts make up the cell wall of diatoms. The pigments are found in the chloroplast of diatoms. Chlorophyll a, chlorophyll c, and xanthophyll are the pigments in the issue. Fucoxanthin is another name for this xanthophyll. Diatoms have a golden colour due to these pigments.Diatoms are usually immotile due to the lack of flagella in their cells. They float on the water's surface due to accumulated fats with a low molecular weight. The slimy secretion aids the movement of certain diatoms. This slimy secretion is made up of an oily substance excreted by diatoms. This serves as a lubricant for the diatoms' movement.Diatoms are naturally autotrophic. In diatoms, food is preserved in the form of leucosin (crysolaminarian) and fats (oils).  There are two types of diatoms. One is round, while the other is elongated. Diatoms are divided into two categories based on their form: pennate diatoms and  centric diatoms.