Wiki > 555 Timer > tim37.gif

Block Diagram

Wiki > 555 Timer > 555-Timer-Block-Diagram.png

Bi-Stable Mode

Wiki > 555 Timer > 555-timer-bistable-mode-768x475.png

Wiki > 555 Timer > 555-timer-monostable-mode-768x468.png

Wiki > 555 Timer > 555-Timer-Astable-Mode-Formulas-Calculations-Time-and-Frequency-768x393.png

Reference	URL
How a 555 Timer IC Works	https://howtomechatronics.com/how-it-works/electronics/555-timer-ic-working-principle-block-diagram-circuit-schematics/