Fritzing Dark Sensor

If there's light, the LDR resistance decreases and the LED is on. If there's no or little light around, the LDR resistance increases and the LED is off. 

Dark sensor on breadboard

Dark sensor schematic

Fritzing Touch Sensor

Our body acts as a resistor, the base of the transistor and the battery gets connceted when touching both ends with a finger. 

Touch sensor on breadboard

Touch sensor schematic

Fritzing Timer 555

Timer 555 is an integrated circuit 

Timer 555 schematic

timer 555 breadboard