In this issue, a wide range of interesting topics is covered. These include documentation of the bacteriostatic properties of melatonin, the effects of melatonin on parasite development inside the host, the protective effects of a combination of melatonin with paclitaxel on ovarian carcinoma cells and the effects of pineal melatonin on the mRNA expression of melatonin and steroidogenic-related receptor genes in the rat reproductive system, etc. We also want to recommend two important research articles that appear in the current issue. One is that of Souza et al. and other is reported by Ko et al. Souza et al. show that melatonin synthesized by microglia plays a key role in the transformation of microglia type 1 (M1) to microglia type 2 (M2) phenotypes.  M1 is responsible for tissue pro-inflammatory reactions and in many cases, it causes the severe tissue damage observed such as in the SARS-CoV2 infection while M2 produce anti-inflammatory actions to cope with injury recovery. This also indicates melatonin administration will help the M1 to M2 transition and suppress the inflammatory tissue injury in many different situations.  Ko et al. report that by using ³¹phosphorus-magnetic resonance spectroscopy (³¹P-MRS), they can directly measure parameters of liver metabolic function in the intact animals and thus, this method can monitor the detailed evolution of liver fibrosis. To the best of our knowledge, this is the first use of ³¹P-MRS for this purpose. In addition, with the aid of this method they observed that when melatonin-pretreated mitochondria are transfused into the blood of the liver-damaged animals, the hepatic fibrosis of the animals is significantly reduced. The results provide a new avenue to target the pathophysiology of the liver fibrosis which currently lacks an effective treatment. We hope that the novel observations reported in the current issue will stimulate the enthusiasm of melatonin scientists to further advance this important field by applying melatonin to other new experimental and clinical situations.