Microplastics and nano-plastics have become a worldwide issue in the aquatic ecosystem. Microplastics contains particles of size ranging from 1 μm to 5 mm, while nanoplastics range from 1 nm to 1 μm. These materials are known to possess sophisticated elementary properties that affect their migration, toxicity, bioavailability, and interactions with surrounding pollutants. In this chapter, methods of analysis, chemical and physical, are discussed in detail. These methods of detection generally involve isolation of the particles from the habitat, and then the tests are run on them. It includes detection methods such as visual and microscopical techniques, spectroscopic techniques, receptor-based techniques, and thermal analysis. The technique involves various methods such as dissecting microscopy, polarized microscopy, fluorescence microscopy, scanning electron microscopy, and atomic force microscopy. Various methodologies are used to obtain images of the MPs and NPs. Spectroscopic technique involves studying the motion of molecular vibration for the detection of material. Another method of detection discussed is receptor-based detection, which provides high accuracy and precision in bio-applications. This method allows for the distinction of MPs and NPs present in the surroundings, as well as the identification of the plastic’s composition. Thermal Analysis involves the identification of MPs and NPs based on the products formed by the thermal degradation of the material. Thermal analysis techniques utilize the analysis of the material obtained from the thermal degradation of the sample to identify the MPs and NPs. Methods such as differential scanning calorimetry (DSC) and pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) are used in thermal analysis. These methods can also be used in combination for the identification process. Recently, there has been a rising concern about the existence of MPs and NPs in the surroundings. This results in the need for standardization of detection methodologies, which can be achieved by creating combinations of available techniques. Additionally, this opens up a new space for research on standardizing detection methods.