The article reviews the advancements in the field of bacterial polyhydroxyalkanoates (PHA) since 1973. PHA is a class of optically active microbial polyesters that include hydroxylacyl monomer units other than 3-hydroxybutyrate (3HB), with the most abundant being PHB. The review highlights the expansion in research areas, including the commercial exploitation of PHAs, their physical properties, and applications. It also discusses the discovery and production of PHAs by various bacteria, such as *Alcaligenes eutrophus* and *Pseudomonas oleovorans*. The article covers the detection, isolation, and analysis methods for PHB and other PHAs, including staining reactions, centrifugation techniques, and spectroscopic analyses. Additionally, it explores the biosynthesis, degradation, and regulation of PHA accumulation, focusing on the enzymes involved in the process, such as 3-ketothiolase, acetoacetyl-CoA reductase, and PHA synthase. The review concludes with a discussion on the future prospects of novel PHAs and their potential in biodegradable plastics.The article reviews the advancements in the field of bacterial polyhydroxyalkanoates (PHA) since 1973. PHA is a class of optically active microbial polyesters that include hydroxylacyl monomer units other than 3-hydroxybutyrate (3HB), with the most abundant being PHB. The review highlights the expansion in research areas, including the commercial exploitation of PHAs, their physical properties, and applications. It also discusses the discovery and production of PHAs by various bacteria, such as *Alcaligenes eutrophus* and *Pseudomonas oleovorans*. The article covers the detection, isolation, and analysis methods for PHB and other PHAs, including staining reactions, centrifugation techniques, and spectroscopic analyses. Additionally, it explores the biosynthesis, degradation, and regulation of PHA accumulation, focusing on the enzymes involved in the process, such as 3-ketothiolase, acetoacetyl-CoA reductase, and PHA synthase. The review concludes with a discussion on the future prospects of novel PHAs and their potential in biodegradable plastics.