The collection of chapters in this book present the concept of matched filters: response characteristics "matching" the characteristics of crucially important sensory inputs, which allows detection of vital sensory stimuli while sensory inputs not necessary for the survival of the animal tend to be filtered out, or sacrificed. The individual contributions discuss that the evolution of sensing systems resulted from the necessity to achieve the most efficient sensing of vital information at the lowest possible energetic cost. Matched filters are found in all senses including vision, hearing, olfaction, mechanoreception, electroreception and infrared sensing and different cases will be referred to in detail.