penetrate into (someone or something)
To pierce, enter into, and stop inside of someone or something. The bullet penetrated into my chest through the body armor, but it thankfully did not pierce my heart or lungs. All kinds of radio waves penetrate into us throughout the day, but none are known to be harmful.
penetrate into someone or something
to pierce into someone or something; to stick deep into someone or something. The lance penetrated into the knight, right through his armor. The bullet penetrated into the wall.