In the talks, I am going to give the definition of triangulated categories and t-structures defined on them if they can be defined. Then a gluing process of two t-structures on two derived categories is introduced, which basically is Theorem 1.4 of the book "Faisceaux Perverses" by Beilinson, Berstein and Deligne. The talks are meant to be an introdcution, so I will make things as self-contained as possible, assuming some axioms or formalism, which can be verified separately depending on the contexts we are working on.