Since Aviram and Ratner first proposed the concept of molecular rectifier in 1974, molecular electronics has received considerable attention due to its promising applications in nanoscale electronics. During the past two decades, many studies have shown that molecules can act as transistors, rectifiers, switches, and optoelectronic devices, indicating that electronic devices based on molecules have the makings of a prototype for next-generation electronics. In this talk, I will give an overview of molecular electronics from a viewpoint of physical chemistry and condensed matter physics. To encourage students to devote themselves to basic scientific research, I will share my research experience and introduce my early-stage research instead of my recent work.