**1. Introduction**

Since the discovery of the first programmable computer, the dependency associated with paper and canvas-based mediums to store and process information has significantly declined. According to Moore's law and Dennard's law, the technology based on the traditional complementary metal-oxide semiconductor (CMOS) has great strides in the last few decades and led to a sharp rise in digital capabilities [1–3]. In traditional computing technology known as Von Neumann architecture, the system comprises two separate units, namely central processing unit (CPU) and data storage unit, connected through the bridge known as data busses. This traditional architecture causes the delay in processing and consumption of more power in the process, introduced as bottleneck of Von Neumann architecture. The memristor has emerged as a novel device to improve or develop new technology based on the fusion of memory and processor. In the last few years, memristor has captured the significant attention of researchers due to its excellent properties, such as simple structure, high-density data storage, low power consumption, fast switching speed, long endurance and retention, multistage and high scalability. Due to these properties, memristors can be used for artificial intelligence (AI), the Internet of Things (IoT), wearable electronics, smart medical applications, logic circuits, neuromorphic computing, etc. [4, 5].

In this chapter, we discuss the history and various switching mechanisms in memristors. Different including organics, inorganics, and hybrid materials have been discussed to use as active layers for memristive applications. Metal halide organic–inorganic perovskites are well taken as an example of hybrid materials due to outstanding electrical, optical, and structural properties. Various applications of memristors, such as data storage, logic gates, and photonic devices, including many bionic electronic systems as artificial synapses, neural networking, nociceptors, artificial retina, etc., have been summarized.
