Diatoms are essentially the "grass" of the ocean. They can not be seen by the naked eye like grass but they play the role like grass. Diatoms possess the ability to convert sunlight and nutrients into living things by the process called photosynthesis. As you know sunlight is the main source of energy so the Diatoms are technically the energy source of the ocean. Little do people know, Diatoms were originated around the Early Jurassic Period. Also, most of them are unicellular types of phytoplankton but they can also exist in colonies as well. I found out that there are two main types of Diatoms, one group are called centric diatoms which are radially symmetric and the other group are called pennate diatoms which are bilaterally symmetric.