Nanotechnology is an emerging technology which has attracted a lot of interest in the last 20-30 years. Indeed many forms of nanostructures have been synthesized and applied in numerous fields which include drug delivery, medical imaging and applications in packaging and energy storage devices. The synthetic approaches which have been employed to prepare these nanostructures include chemical vapour deposition, laser ablation and arc discharge techniques. However, hydrothermal techniques have become increasingly more popular over the years. This talk therefore focuses on the principles of hydrothermal techniques and how these methods have been utilized to yield novel nanostructures which have been successfully employed in numerous applications. Emphasis is placed on applications in water treatment where nanostructured adsorbents have been prepared and used for the removal of numerous pollutants from wastewater. The use of nanostructured catalysts in the photocatalytic degradation of organic pollutants is also highlighted. Specific studies which will be discussed include the use of nanocabbages as photocatalysts in the photocatalytic degradation of methylene blue. The talk also highlights use of nanostructures in forensic applications such as in latent fingerprint detection. In this sense a study on the use of ZnO nanoparticles coated onto carbon dots synthesized from potato peel waste and used in finger print detection is discussed in detail. The talk concludes with some perspectives on how nanostructured materials prepared by hydrothermal techniques can help us in developing smart sensors for solving real life problems in South Africa and across the globe as we move forward into the Fourth Industrial Evolution Era.