Mitochondria are involved in a number of cellular functions, which ensure that our cells, tissues and organs function efficiently and provide the individual with the necessary metabolic resources to undertake normal daily functions. It is becoming evident that mitochondrial dysfunction and mutation and abnormal regulation of the mitochondrial genome (mtDNA) can lead to an increasing number of severe metabolic disorders which are not only specific to single tissues or organs but also lead to multisystem disorders. Here, we analyse the role that mitochondria and mtDNA play in fertilisation and developmental outcome in order that we have a better understanding of how the efficient regulation of mitochondria and mtDNA during very early development ensure that an individual is born healthy and maintains a normal healthy lifestyle.