The water cycle.
The way ice floats (instead of sinking).
The way a tree's roots spread out and hold the soil in place.
The way seeds are designed to be able to travel away from a bigger tree.
The way a bird knows how to build a perfect, little, round, nest from mud and sticks.
The way a mother's breasts create milk.
The way a newborn baby already knows how to suckle.
That's just what I can come up with off the top of my head.
The list goes on and on.
For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse. Romans 1:20