How are God's invisible attributes seen and understood through creation?

God has shown what may be known of Himself to all people, making it manifest in them. From the creation of the world His invisible things are clearly seen and understood by the things that are made, namely His eternal power and Godhead, so the whole human race is without excuse.

Les explains that Romans 1:19 says what may be known of God is manifest in them, for God hath shown it unto them, and he notes this is past tense—it is already done. He compares it to John 1:9, where the light lighteth every man that cometh into the world. Paul says basically the same thing: the invisible things of God from the creation of the world are clearly seen and understood by the things that are made, even His eternal power and Godhead. The result is that the whole human race is without excuse, and no one will ever be able to say to God, 'But I never had a chance.'

Romans 1:20

For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:

How can people see God's invisible qualities like His eternal power and Godhead?

According to Romans 1, God's invisible qualities—His eternal power and Godhead—are clearly seen from the creation of the world. They are understood by the things that are made, because God has manifested that knowledge in people, leaving the whole human race without excuse.