Conventional paper is composed of cellulose fibres randomly arranged in a network with micro-sized air cavities. As the size of the fibres is much larger than the optical wavelength, the incident light is scattered, and the regular paper is opaque. Paper is known for its flexibility and recyclability, lightweight and low cost. Cellulose-based materials in the last years have been used in several applications due to their non-toxicity and biodegradability and have been presented as a good resource to tackle the waste crisis. Nowadays, transparent paper, introduced in the nineteenth century, has been pointed out as a suitable alternative to regular paper and to petroleum-based substrates. The transparent paper has better mechanical properties, higher surface, lower porosity and better optical properties compared to conventional paper and produces less pollution when compared to plastic. Transparent paper, or nanopaper, from different cellulose and chitin sources, can be produced using similar techniques and solvent systems. The present chapter portrays transparent paper as viable and valuable resource, owing to its printability, flexibility and stability at high temperatures, to be used in diverse applications, such as flexible electronics, touch screens, biomedical sensing and packaging.