A monorhyme is a very simple poem in which all of the lines end with the same rhyming sound.
Smiling
Do you find it amazing
That the simple act of smiling
Can be so invigorating
As we stand about watching
Young children playing
Or spend a moment listening
To all the birds singing
And anyone who may be viewing
Our delighted faces expressing
What we are deeply feeling
Will immediately stop frowning