Sergei Skripal case: what do nerve agents do and how hard are they to make?

After days of analysis, police investigators announced on Wednesday that they believe a nerve agent was used to poison former Russian agent Sergei Skripal and his daughter on Sunday, raising questions of how it was created and how the attack was carried out.A range of highly potent nerve agents were developed by military scientists from the 1930s onwards and a number have since been used in assassinations and terror attacks.The Malaysian authorities have charged two women with Kim’s murder