Pimoroni Explorer HAT Pro

This module is used to extend the Raspberry's 40 GPIO pins to another set of 2x20 male pins and 8 parallel pins accessible on the terminal blocks in the that test leads are pushed. The electronic board offers great reliability with the Raspberry and is very easy to connect thanks to its existing suitable accessories but not included.
The module offers a set of mini jumpers to configure the GPIO.

This HAT is an open source portable sensor that provides the level of suspended particulate matter quantity with its mass. It has a powerful and high-tech PMSA003 sensor that provides the information of suspended particulate matter (PM1.0, PM2.5, PM10) in the air per unit volume.

QWIIC is a connection standard developed by Sparkfun enabling a quick an easy connection of peripherals without a need to solder pins, without any mismatches due to polarized connector. And on top of that you can "daisy chain" them! 

This hat pretty much opens the whole QWIIC universe in front of your Pi. It features 4 QWIIC ports all on the same I2C bus (GND, 3.3V, SDA, and SCL).

A universal  2x20 GPIO makes it compatible with all Raspberry Pi boards, as well as Google Coral and Jetson Nano.

Note:  For a secure connection in some applications, you'll need to add a pair of 1x20 stackable headers to extend the pins to your cart.

Pimoroni Fan is the best you can do for your new Raspberry 4! It is a well known fact, Raspberries can get hot. Even though, there are plenty of solutions to that, you will find no better than this Pimoroni Fan. It is a no-solder device, hence you can put it on and off as you wish

T-Cobbler Protoboard Extension Plate GPIO 40 Raspberry PI B+ Pin features:
- Shield expansion module for Raspberry Pi 2 and Pi 3, B and B +
- Dimension: 6 x 7.3x 1.9mm

Pimeroni Unicorn HAT is one of the most popular and at the same time easiest to use Raspberry HATs in Pimoroni offering. It is featured with a matrix of 64 RGB LEDs powered directly through the Pi board. The applications of the HAT spread from just a simple games in the classroom up to color indications in your robot. All of this accessible in a really straight forward way and supported by a range of Python libraries available on github and officially issued by Pimeroni. The hat is compatible with all Raspbery boards given its universal 40 GPIO pinout

Raspberry Pi Pico HAT Expansion is an input/output expansion board designed for Raspberry Pi Pico, which provides a set of 2x20 pin headers in the form of Raspberry Pi header along with a set of 2 x 20 pins. It allows any HAT designed for Raspberry Pi to be connected to Raspberry Pi Pico.

Can't stand to run out of pins in your Raspberry Pi? You have a cool new accessory but there's no way to plug it in? If you answered yes to any of the above, then this pHAT could be just for you. This piece has 6 sets of 40 GPIOS - one for your Pi and the rest (5) for your collection of HATs that you might want to plug in at the same time. Use it for a specific project or just to play with several HATs at once.  

The Grove Starter Kit for Arduino is one of the best Arduino starter kits for beginners. It includes an Arduino-compatible base shield and 14 additional Arduino sensors and accessories. With this Grove starter kit, you can create any Arduino project you want.

Controls 4 devices and loads up to 240V AC / 7A, 30V DC / 10A, a way to control high voltage / current devices. Helps the user to improve the intelligence of the devices. It consists of an "Optocoupler".