Biotechnology plays an increasingly important role in the twenty-first century. In the past few decades, a wide variety of biosynthesis processes have been developed and applied throughout the pharmaceutical industry, agriculture, food, energy, chemical industry, and many other fields. This article briefly introduces the recent progress in cellular systems in bioprocesses, including bacteria, yeasts, filamentous fungi, algae, plant cells, and animal cells. It also covers stem cells and man-made artificial cells, which develop rapidly and show promising potential in future therapy of human diseases. The emphasis has been mainly focused on heterologous protein expressions and the production of biochemicals, biofuels, and biopolymers using various cellular systems. The cell culture conditions, for example, solid-state fermentation and immobilized cell fermentation, are also discussed. It is expected to significantly reduce the energy consumption and carbon dioxide emission by applying bioconversion processes using either whole cells or enzymes produced from cells.