This book is divided into two parts: the foundation part (Chap. 2) and the application part (Chaps. 3–5). In Sect. 2.3.1, we start from an easy application of inequalities to derive a very first bound. We then study finding distinct elements in Sect. 2.3.2 We show an insight to solve the problem and how to analyze the insight. In Sect. 2.3.3, we present a two cat problem and we develop an algorithm that is sublinear, yet differs from the traditional (1 +ε, δ) sublinear algorithm format. We then look into three applications of sublinear algorithms on wireless sensor networks, big data processing, and smart grids in Chaps. 3–5.