The top row of keys on any MacBook or Mac keyboard are dedicated to basic computer controls -- media controls, keyboard backlight brightness, screen brightness, volume, Mission Control, Launchpad and power.
Screen brightness and volume controls are easily the most frequented keys on that row. By default there are 16 increments for adjusting brightness or volume levels. But what if the perfect volume or brightness is somewhere between one of the 16 steps?
A life protip from Reddit user WinstonSmith87 answers exactly that.
LPT: Holy crap. Shift + alt lets you do 'in between' volumes/brightness on a mac. from LifeProTips
Holding Shift and Option while toggling volume or screen brightness allows you to adjust the levels in quarter increments, giving you a total of 64 possible steps for both brightness and volume.
As a bonus, you can hold Option while pressing any of the brightness keys (including keyboard brightness), volume keys or Mission Control to open the respective submenu in System Preferences. And holding only Shift while pressing volume up or down will play audible clicks for each volume adjustment.