**2. 2D cell cultures**

2D cell cultures have been the main type of cell cultures used by scientists in various fields for decades [6]. As explained in the introduction, cell cultures that grow in controlled flat environments, such as a Petri dish, are 2D cell cultures [6]. To maintain cells outside of an organism's body, it is important to have the correct equipment and supplies to ensure the provision of an environment in which cells can survive and divide [2, 3]. Equipment involved typically includes a biosafety hood for maintaining the safety of cultures and of the individuals working with the cultures, a cell incubator for correct storage with a temperature of 37°C and 5% levels of CO2 , a refrigerator for culture media and other supplies, and flasks or Petri dishes for placement of cells, amongst other required equipment [2, 3].

Besides having the correct equipment for adequate handling and storage of cell cultures, the culture medium or environment in which cell culture grow is also important. The cell culture medium in 2D cell cultures initially consisted of blood plasma; however, over the years, synthetic medium with the right amount of nutrients and even antifungal and antibiotic ingredients have been developed [11]. Cell culture medium is expected to contain amino acids, a buffering system, vitamins, trace elements and more, to maintain cell viability [12]. Eagle's minimum essential medium (EMEM) and Dulbecco's modified Eagle's medium (DMEM) are two examples of cell culture media that have been developed [13]. Different cell types may require different culture media, and thus, the nutrient requirements may vary [13].
