Plastic products have countless applications in all areas of our everyday life. The tremendous economic success of plastics is based on its low production costs in combination with its versatile material properties. Its durability, together with an inadequate disposal followed by fragmentation due to weathering or abrasion of particles from plastic products during usage, led to an ongoing accumulation of microscopically small plastic particles, so-called microplastics in terrestrial and aquatic ecosystems. Various organisms from all environmental compartments, including humans, frequently encounter and internalize these microplastics. Once internalized, microplastics may have adverse effects on organisms. Interaction with an organism and effects of microplastics are diverse and are found on different levels of biological organization from the whole organism over tissues down to single cells. In this book chapter, we address the occurrence and fate of microplastics in the environment and focus on possible impacts of microplastics on environmental and human health. In relation to the focus of this chapter, we further discuss future perspectives in microplastic research.