Lichens are symbionts that inhabit a wide range of ecological conditions on Earth, ranging from hot and humid tropical rainforests to cold alpines and polar ecosystems. In this symbiotic association, a fungus and a photosynthetic partner, either green algae or cyanobacteria, live in a distinctive symbiotic relationship and thrive well by mutually exchanging food, nutrients, and shelter between fungus and phototroph. In contrast to other fungal symbiotic association, lichens form noticeable and easily identifiable macroscopic vegetative thalli that display a range of diverse colors and different morphologies. Although this symbiotic association has successfully been studied for many years, very little information is available about the physiological and molecular mechanisms operating in this stable symbiotic association. This chapter will firstly give a brief account of the evolution that this symbiotic association has undergone. Moreover, it addresses the metabolic pathways and signaling and recognition mechanisms between the photobiont and the mycobiont. This chapter provides an overview of the steps that have been made thus far to apply the function of omics approaches, including transcriptomics, metabolomics, genomics, and so on, in understanding the regulation, signaling, and metabolism of lichen symbiosis. Thus, a stronger comprehension of this association will result from this.