Epigenetics and avian influenza virus are two research fields subject to intensive studies and attracted much attention in recent years. Several interesting reviews and research articles well-organized into these topics were published in the 2009 edition No.4 and No.5 of Science in China Series C-Life Sciences (SCLS). The topic “Molecular epigenetics: dawn of a new era of biomedical research” consists of three review papers, which summarized the latest advances and perspectives in three different fields of molecular epigenetics, including the inheritance of histone methyl marks as well as the dynamic regulation of histone methylation by demethylation, the microRNA biogenesis and the mechanism by which microRNA function in post-transcriptional gene silencing, and RNA-directed DNA methylation and demethylation in plants. The topic entitled“The challenges of avian influenza virus: mechanism, epidemiology and control” contains seven review articles, one research paper and one website introduction. These papers concentrated not only the clinical aspects of avian influenza virus infection in China, but also the basic research in this field, which gave us a full picture on the spread of H5N1 virus, as well as how to combat it in China. These articles on H5N1 would be highly meaningful not only for scientists but also for ordinary people.