There are many English phrasal verbs that use 'in'. Here is a selection of some of the more common.
break in (1) = interrupt: "He broke in to their conversation to add that he couldn't work overtime."
break in / into (2) = burgle / steal: "Thieves broke into the warehouse and stole 100 computers."
bring in (1) = introduce: "She has brought in some changes to the company."
bring in (2) = receive income: "He brings in a lot of money as a computer programmer."
cave in = accept someone's idea or decision: "The unions finally caved in and accepted the new contracts."
chip in = contribute: "We're all chipping in for Maria's birthday present."
fill in (1) = complete: "You need to fill in this form."
fill in (2) = act as a substitute: "As Robert is on holiday, you'll have to fill in for him this week."
fill in (3) = bring someone up to date: "Can you fill me in on the new project?"
fit in = be accepted by a group: "He doesn't really fit in at work. He's very different from us."
give in = finally accept something: "She gave in to her children's demands for sweets."
hand in = give something to someone: "They handed in their assignment early."
kick in = start to have an effect: "The painkillers have finally kicked in. I feel much better."
lead in = start with something: "In our presentation, we are going to lead in with our vision for the future."
move in = occupy a house: "Some new neighbours have moved in next door."
take in (1) = understand: "I still can't take in the news."
take in (2) = deceive someone: "He really took me in with his hard-luck story."
take in (3) = provide refuge: "She took the old couple in."
work in = incorporate: "Is there any way of working in this paragraph? The text is a little unclear otherwise."