情，qíng，sentiment, emotion 情 = 忄 + 青. It is usual to see in this association the heart （in composition it can be written 忄) and 青 qing, phonetic element. Certainly, 青 gives the pronunciation. When we remember that 青 also means young, we can make the connection between youth and feelings, the ardour of the feelings of youth. At the same time, this way of looking at the structure of the character helps to remember the composition better.
The character 思 sī, to think, is formed by, 心 xīn, heart and 田 tián, field. Bizarre? Yes and no. For aesthetic reasons or convenience or for fluidity in writing with the brush, some characters have lost a line, a dot, or have even given way to others. Let’s go back to the origin of 思 :
An ancient writing includes the heart at the bottom and the brain: . The brain handles reason, and the heart controls feelings. 囟 xìn has a sense of fontanelle. It has lost its place over the centuries to 田, which is simpler to write.