Food dehydration is still one of the most relevant and challenging unit operations in food processing, although the art of food preservation through the partial removal of water content dates back several centuries. This article provides essential information on the fundamental. including psychrometry, and applied engineering aspects of food dehydration with up-to-date available commercial applications. The evolution of drying technology, divided into four generations, is thoroughly reviewed, from tray drying to the combination of some drying technologies (the hurdle technology approach in drying) in order to optimize the process in terms of final food quality and energy consumption. The study of each generation covered numerous examples of different dryers. including their principles of operation, basic configurations and most common applications, as well as their main advantages and disadvantages.