If you connect the capacitor in backwards, or you connect a larger voltage than the rating for that capacitor, then there is a good chance it will “pop” like a firecracker. In the picture, you can see three capacitors, one with the large white stripe.

And this stripe usually has large minus signs. The aluminum can that holds the capacitor together will have a large stripe on the cathode side. The shorter electrode is the “cathode” and should be connected to the zero volts (ground). On these capacitors the longer electrode is the “anode” and should be connected to the positive voltage. Electrolytic capacitors are polarized, meaning it is important which electrode is connected to the positive voltage and which is connected to ground. Likely if you are trying out this project, you are somewhat new to electronics. Solderless breadboard, 140-point size or bigger.

Electrolytic capacitor, one or more, 10 uF but any value would do.

Resistors, two or more, any values between 1kOhm to 1MOhm will do.

Download 555 timer pinout