Light signaling in plants has been a central focus of research for over a century, revealing the molecular mechanisms by which plants perceive and respond to light. The discovery of phytochrome, a light-sensitive protein that absorbs red and far-red light, was pivotal in understanding how plants regulate growth and development. Phytochrome exists in two interconvertible forms, Pr (red-light absorbing) and Pfr (far-red-light absorbing), which trigger different physiological responses. The identification of phytochrome's structure and function, along with its role in gene expression and developmental processes, has been crucial in elucidating light signaling pathways. Cryptochromes, another class of light-sensitive proteins, were identified later and are involved in blue light signaling. They share structural similarities with DNA photolyases but function as signaling photoreceptors rather than DNA repair enzymes. Cryptochromes regulate gene expression and photomorphogenesis, interacting with various signaling proteins and transcription factors to modulate plant development. The CRY-COP1/SPA axis is a key mechanism in plant cryptochrome signaling, where cryptochromes inhibit the activity of the E3 ubiquitin ligase complex, leading to the accumulation of transcription factors that promote photomorphogenesis. Both phytochromes and cryptochromes play essential roles in light signaling, with phytochromes involved in red and far-red light responses and cryptochromes in blue light responses. These photoreceptors interact with other signaling molecules, such as transcription factors and kinases, to regulate gene expression, chromatin remodeling, and other cellular processes. The molecular mechanisms underlying these interactions have been extensively studied, revealing the complex network of signaling pathways that enable plants to adapt to their environment. The understanding of these pathways has advanced significantly, highlighting the importance of light signaling in plant growth, development, and environmental adaptation.Light signaling in plants has been a central focus of research for over a century, revealing the molecular mechanisms by which plants perceive and respond to light. The discovery of phytochrome, a light-sensitive protein that absorbs red and far-red light, was pivotal in understanding how plants regulate growth and development. Phytochrome exists in two interconvertible forms, Pr (red-light absorbing) and Pfr (far-red-light absorbing), which trigger different physiological responses. The identification of phytochrome's structure and function, along with its role in gene expression and developmental processes, has been crucial in elucidating light signaling pathways. Cryptochromes, another class of light-sensitive proteins, were identified later and are involved in blue light signaling. They share structural similarities with DNA photolyases but function as signaling photoreceptors rather than DNA repair enzymes. Cryptochromes regulate gene expression and photomorphogenesis, interacting with various signaling proteins and transcription factors to modulate plant development. The CRY-COP1/SPA axis is a key mechanism in plant cryptochrome signaling, where cryptochromes inhibit the activity of the E3 ubiquitin ligase complex, leading to the accumulation of transcription factors that promote photomorphogenesis. Both phytochromes and cryptochromes play essential roles in light signaling, with phytochromes involved in red and far-red light responses and cryptochromes in blue light responses. These photoreceptors interact with other signaling molecules, such as transcription factors and kinases, to regulate gene expression, chromatin remodeling, and other cellular processes. The molecular mechanisms underlying these interactions have been extensively studied, revealing the complex network of signaling pathways that enable plants to adapt to their environment. The understanding of these pathways has advanced significantly, highlighting the importance of light signaling in plant growth, development, and environmental adaptation.