Transition...ing

1

a : passage from one state, stage, subject, or place to another : change b : a movement, development, or evolution from one form, stage, or style to another
2

a : a musical modulation b : a musical passage leading from one section of a piece to another
3

: an abrupt change in energy state or level (as of an atomic nucleus or a molecule) usually accompanied by loss or gain of a single quantum of energy

~websters dictionary