Since rheology is quite a young science, there are still a lot of issues to be studied, observed and explored. This book is intended to inspiring and stimulating engineers, material scientists, chemists, mathematicians or their teams to find out a beauty of rheology, possibilities of its exploitation and excitement of the rheological investigation. Built up upon the fundamentals, existing tools used, or the tools elaborated by author, four themes are explored in more detail: 1. biological material – human plantar aponeurosis tissue under the creep test and relaxation test; 2. viscoelastic structure subject to a dynamical load; 3. viscoelastoplastic model of concrete; 4. dissipation of energy as one of the decisive factor justifying or not, the linear approach in subsequent investigation. Conditional stiffness, Duhamel hereditary integrals, time dependent moduli, Prony series, variation inequalities, etc., are used as tools herein. Everything is built up on fundamentals, thermodynamic consistency is required and examined.