Explain surah hajj verse 5

In Surah hajj verse 5 Allah, the exalted, tells us about the creation of human. In the verse it says we have created the human from clay then Nutffa (sperm) then flesh... my question is Allah is talking about who Adam or humans because Adam can´t be created from Nuttfa because he was the first human. If Allah is talking about humans then how can humans made from clay because humans are first made from (sperm). Can you explain? jazzaakAllah...