Microplastic (MP) is an important topic in our world. More and more plastic is produced and can be found in nature. It's not only the plastic we can see as bottles, bags or other waste. There is a lot more in form of tiny pieces. Scientist found MP in almost any part of our environment – oceans and rivers, soil and also in animals and our water bottles. There are studies showing that MP can have negative impact on the metabolism of animals and even cause their death. It is most likely that humans also suffer from MP in the future. To find solutions for this problem you have to understand it at first. Therefore, the topic can be divided into three aspects. The first one is the development. In most cases the MP lifecycle actually starts with macroplastic. Big parts, especially packaging material, get into nature by littering. There they are exposed to different kinds of stresses like UV radiation, fluids and mechanical stress. In the past there have been many studies that analyze single aspects like the influence of UV radiation on the strength of plastics. But there is no deeper inside into the fracture mechanisms of plastics under the combination of the variety of natural stresses. The Environmental Stress-Cracking Resistance (ESCR) of the polymer of a component plays an important role in the kinetics of the degradation into MP. This will be specially adressed in this contribution. The second aspect of MP is the transport of the particles. Once MP is built it can spread by many transport mechanisms because of its very low size. Wind, water and even animals are part of the transport process. The last aspect are the biological effects. Until know it has been seen that MP could harm animals. But it is not clear, if any type of plastic, any geometry, size or surface property is particularly dangerous. This shows that there are many open questions giving space for interesting investigations and can guide us to avoidance or reduction of MP.