An understanding of oocyte and embryo metabolism is critical to understanding and developing in vitro culture systems. In the last 60-70 years there has been a constant evolution in the way metabolism studies have been conducted. This includes a change from studying the metabolism of the oocyte alone vs. as a whole cumulus oocyte complex. The study of in vivo environments has lead to the creation of defined sequential culture systems, resulting in overcoming developmental blocks and improved embryo development. And techniques for studying metabolism have evolved from the use of radiolabelled isotopes to increasingly specific fluorescence probes and metabolomics, allowing for large, integrative profiles. Metabolism is a potential diagnostic for selecting the most likely embryos to implant. We envisage the future of metabolism will involve the ability to measure ‘morein-less’ (more substrates, less volumes) and allow for a holistic approach to understanding the relationship between metabolism and developmental competence, as it is unconceivable that a single metabolic output will be able to assess health and/or quality