All the CubeSat components will be housed in the structure, which must be strong enough to ensure that the satellite safely reaches orbit. There are several methods to reach low Earth orbit, but the most common method for CubeSats is to piggyback on another rocket as a secondary payload. During launch, rockets are subject to very large forces and vibrations.
On Earth, we are protected by an atmosphere. In low Earth orbit, the atmosphere is below us and that protection is no longer present. Satellites are subject to intense thermal radiation, such as direct solar energy, albedo (solar energy reflected off the Earth), and infrared energy produced by the Earth itself. Keeping the CubeSat and its components within operational temperature ranges is achieved by maintaining a thermal balance throughout the satellite.