In 1965, Kushnirenko introduced the notion of sequence entropy along a given sequence of nonnegative integers for a measure-theoretical dynamical systems (MDS). He showed that an invertible MDS has discrete spectrum iff every sequence entropy of the system is zero. Following Kushnirenko's work, Saleski gave a characterization of weakly mixing and strongly mixing MDS via sequence entropy. In 1974, Goodman introduced the notion of topological sequence entropy and studied some properties of null systems which are defined as having zero topological sequence entropy for any infinite sequence. The characterization of topological weak mixing was also obtained through sequence entropy. This seminar aims to provide the state-of-the-art of sequence entropy of dynamical systems, both in measure-theoretical and topological aspects. Beginning with some fundamental results of sequence entropy, we will propose open problems for those interested participants who would like to have join works.