Light is the main source of energy for life on Earth, and plants and algae are able to convert light energy, through photosynthesis, into chemical energy that can be used by all organisms. The photosynthetic reactions are housed in the chloroplasts, but the chloroplasts also are the site for synthesis of essential compounds like fatty acids, vitamins, amino acids, and tetrapyrroles. Given their essential role, the correct formation and function of chloroplasts is vital for the growth and development of plants and algae, and hence for almost all organisms. Chloroplasts evolved from an endosymbiotic event where a photosynthetic prokaryotic organism was acquired by a proeukaryotic cell. With time, the photosynthetic prokaryote lost or transferred most of its genes to the host genome. As a result, plastid protein complexes, such as the photosynthetic complexes, are encoded by genes of both the nuclear and plastid genomes. This division of genetic information requires a precise coordination between the two genomes to achieve proper plastid development and function. Plastid development and gene expression are under nuclear control, in what is referred to as anterograde control. However, there also is a signaling system originating in the plastids, so-called retrograde signals, transmitting information about the developmental and functional state of the plastids to the nucleus to regulate nuclear gene expression. Retrograde signaling is a complex network of signals that can be divided into “biogenic control,” referring to signals generated by the plastid as it develops from a proplastid or etioplast into a chloroplast, and “operational control” signals, including those generated from a mature chloroplast in response to environmental perturbations (Chan et al., 2016).