Several sugars are essential molecules for all extant life as building blocks of DNA and RAN and the source molecule of glycolysis. Thus, their abiotic origins have been investigated for a long time, with the motivation related to the origin of life. Formose reaction, which is a polymerization reaction of formaldehyde in alkaline solutions, has been regarded as the most plausible reaction that forms sugars on prebiotic Earth. Formose reaction yields diverse sugars, causing challenges in its product analysis. A recent study investigated the effects of pH, temperature, and glycolaldehyde concentrations on the formose reaction and showed that ribose and glucose form even in neutral solutions. This suggests that ribose and glucose could be formed even in the open ocean on late Hadean Earth. Ribose and glucose could also be provided from space via meteorites. Thus, ribose and glucose were available molecules on prebiotic Earth, even though their estimated abundance is low. The absence of deoxyribose suggests a linkage between prebiotic molecules and the RNA world.