Approach notes are an essential element in the construction of improvised lines. They are either chormatic or scale tones that lead up to or surround (approach) a targeted note, usually a chord tone.
The following example uses chromatic approach notes in four places:

• Leading into measure one are a double chromatic approach from above to Bb, the thrid of G-7.
• At the end of measure one, a double chromatic approach from below to E, the third of C7.
• At the end of measure two, a double chromatic approach from below to A, the third of F (I sense a pattern here, hmmm...).
• In measure three, the F on beat four is approached from above and below by single chromatics.

In the first two instances, the approach notes target a strong chord tone on a strong beat. The last two approach strong chord tones on off beats, which is unexpected (therfore surprising and interesting—good qualities in a solo).

That the first approach note at the end of measure one is also a chord tone reinforces the strength of the resolutions.

Another significant factor at work here is the presence of the seventh of the G-7 (F) before the approach notes in measure one. In a ii-7 V7 I progression the natural resolution of the seventh of the minor chord to the third of the dominant chord. That is happening in this example, but the approach notes delay the resolution by one beat. The same thing happens at the end of measuer two (the seventh of the dominant resolves to the third of the major).

The effect is almost that of having a single chromatic above the targeted note along with the double chromatic approach from below. In this case, the resolution patterns make a stronger case for just thinking of it as a double chromatic approach from below.