\scriptstyle - Used to over-ride automatic style rules and force script style.
{ \scriptstyle ...}
\scriptstyle command is used to over-ride automatic style rules and force script style. Stays in force until the end of math mode or the braced group, or until another style is selected.
\frac ab+\displaystyle\frac ab+\textstyle\frac ab+\scriptstyle\frac ab+\scriptstyle\frac ab
\frac ab + {\scriptstyle \frac cd + \frac ef} + \frac gh
\frac ab + \scriptstyle{\frac cd + \frac ef} + \frac gh